diff --git a/README.md b/README.md
index e8acfba..809ab73 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,153 @@
-# FastAPI Application
+# Freelancer Invoicing API
 
-This is a FastAPI application bootstrapped by BackendIM, the AI-powered backend generation platform.
+A professional invoicing API for freelancers and small businesses built with FastAPI and SQLite.
+
+## Features
+
+- Secure authentication system with JWT tokens
+- Client management (CRUD operations)
+- Invoice management with line items
+- Automatic total calculation
+- PDF generation for invoices
+- Activity logging
+- Data protection (users can only access their own data)
+- CORS support for all domains
+
+## Project Structure
+
+```
+freelancerinvoicingapi/
+├── app/
+│   ├── api/
+│   │   ├── endpoints/        # API route handlers
+│   │   │   ├── auth.py       # Authentication endpoints
+│   │   │   ├── clients.py    # Client management endpoints
+│   │   │   ├── invoices.py   # Invoice management endpoints
+│   │   │   └── users.py      # User endpoints
+│   │   ├── deps.py           # Dependencies for routes
+│   │   ├── health.py         # Health check endpoint
+│   │   └── routes.py         # Route registration
+│   ├── core/
+│   │   ├── config.py         # Application configuration
+│   │   ├── logging.py        # Logging setup
+│   │   └── security.py       # Security utilities
+│   ├── crud/
+│   │   ├── crud_client.py    # Client CRUD operations
+│   │   ├── crud_invoice.py   # Invoice CRUD operations
+│   │   └── crud_user.py      # User CRUD operations
+│   ├── db/
+│   │   ├── base.py           # Database models import
+│   │   ├── base_class.py     # Base class for models
+│   │   └── session.py        # Database session
+│   ├── models/
+│   │   ├── client.py         # Client model
+│   │   ├── invoice.py        # Invoice and InvoiceItem models
+│   │   └── user.py           # User model
+│   ├── schemas/
+│   │   ├── client.py         # Client schemas
+│   │   ├── invoice.py        # Invoice schemas
+│   │   ├── token.py          # Token schemas
+│   │   └── user.py           # User schemas
+│   ├── services/             # Business logic services
+│   └── utils/
+│       └── pdf.py            # PDF generation utility
+├── migrations/               # Alembic migrations
+│   ├── versions/             # Migration scripts
+│   ├── env.py                # Alembic environment
+│   └── script.py.mako        # Migration script template
+├── storage/                  # Storage directory
+│   ├── db/                   # Database files
+│   ├── logs/                 # Log files
+│   └── pdfs/                 # Generated PDFs
+├── alembic.ini               # Alembic configuration
+├── main.py                   # Application entry point
+└── requirements.txt          # Dependencies
+```
+
+## API Endpoints
+
+### Authentication
+
+- `POST /api/v1/auth/register` - Register a new user
+- `POST /api/v1/auth/login` - Login to get access token
+
+### Users
+
+- `GET /api/v1/users/me` - Get current user info
+- `PUT /api/v1/users/me` - Update current user
+
+### Clients
+
+- `GET /api/v1/clients` - List all clients
+- `POST /api/v1/clients` - Create a new client
+- `GET /api/v1/clients/{client_id}` - Get a client
+- `PUT /api/v1/clients/{client_id}` - Update a client
+- `DELETE /api/v1/clients/{client_id}` - Delete a client
+
+### Invoices
+
+- `GET /api/v1/invoices` - List all invoices
+- `POST /api/v1/invoices` - Create a new invoice
+- `GET /api/v1/invoices/{invoice_id}` - Get an invoice
+- `PUT /api/v1/invoices/{invoice_id}` - Update an invoice
+- `DELETE /api/v1/invoices/{invoice_id}` - Delete an invoice
+- `POST /api/v1/invoices/{invoice_id}/items` - Add an item to an invoice
+- `DELETE /api/v1/invoices/{invoice_id}/items/{item_id}` - Remove an item from an invoice
+- `GET /api/v1/invoices/{invoice_id}/pdf` - Generate and download a PDF for an invoice
+
+### Health Check
+
+- `GET /health` - Check API health
+
+## Getting Started
+
+### Prerequisites
+
+- Python 3.8+
+- pip
+
+### Installation
+
+1. Clone the repository
+2. Install dependencies:
+
+```bash
+pip install -r requirements.txt
+```
+
+3. Run the migrations:
+
+```bash
+alembic upgrade head
+```
+
+4. Start the application:
+
+```bash
+uvicorn main:app --reload
+```
+
+The API will be available at http://localhost:8000.
+
+API documentation is available at:
+- Swagger UI: http://localhost:8000/docs
+- ReDoc: http://localhost:8000/redoc
+
+## Database
+
+The application uses SQLite as its database. The database file is stored in the `/app/storage/db` directory.
+
+## Security
+
+- JWT token-based authentication
+- Password hashing with bcrypt
+- User-specific data isolation
+- HTTPS recommended for production
+
+## PDF Generation
+
+The application uses ReportLab to generate PDF invoices, which can be downloaded by clients.
+
+## Logging
+
+Activity logs are stored in the `/app/storage/logs` directory.
\ No newline at end of file
diff --git a/alembic.ini b/alembic.ini
new file mode 100644
index 0000000..0f85975
--- /dev/null
+++ b/alembic.ini
@@ -0,0 +1,106 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrations
+
+# template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
+# Uncomment the line below if you want the files to be prepended with date and time
+# see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
+# for all available tokens
+# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
+
+# sys.path path, will be prepended to sys.path if present.
+# defaults to the current working directory.
+prepend_sys_path = .
+
+# timezone to use when rendering the date within the migration file
+# as well as the filename.
+# If specified, requires the python-dateutil library that can be
+# installed by adding `alembic[tz]` to the pip requirements
+# string value is passed to dateutil.tz.gettz()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; This defaults
+# to migrations/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path.
+# The path separator used here should be the separator specified by "version_path_separator" below.
+# version_locations = %(here)s/bar:%(here)s/bat:migrations/versions
+
+# version path separator; As mentioned above, this is the character used to split
+# version_locations. The default within new alembic.ini files is "os", which uses os.pathsep.
+# If this key is omitted entirely, it falls back to the legacy behavior of splitting on spaces and/or commas.
+# Valid values for version_path_separator are:
+#
+# version_path_separator = :
+# version_path_separator = ;
+# version_path_separator = space
+version_path_separator = os  # Use os.pathsep. Default configuration used for new projects.
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+# SQLite URL
+sqlalchemy.url = sqlite:////app/storage/db/db.sqlite
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+# hooks = black
+# black.type = console_scripts
+# black.entrypoint = black
+# black.options = -l 79 REVISION_SCRIPT_FILENAME
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S
\ No newline at end of file
diff --git a/app/api/deps.py b/app/api/deps.py
new file mode 100644
index 0000000..e43ef41
--- /dev/null
+++ b/app/api/deps.py
@@ -0,0 +1,41 @@
+from fastapi import Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordBearer
+from jose import jwt, JWTError
+from sqlalchemy.orm import Session
+from app.db.session import get_db
+from app.models.user import User
+from app.core.config import settings
+from app.core.security import ALGORITHM
+from app.schemas.token import TokenPayload
+
+oauth2_scheme = OAuth2PasswordBearer(tokenUrl=f"{settings.API_V1_STR}/auth/login")
+
+
+def get_current_user(
+    db: Session = Depends(get_db), token: str = Depends(oauth2_scheme)
+) -> User:
+    """
+    Get the current user based on the JWT token.
+    """
+    credentials_exception = HTTPException(
+        status_code=status.HTTP_401_UNAUTHORIZED,
+        detail="Could not validate credentials",
+        headers={"WWW-Authenticate": "Bearer"},
+    )
+    try:
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[ALGORITHM]
+        )
+        user_id: str = payload.get("sub")
+        if user_id is None:
+            raise credentials_exception
+        token_data = TokenPayload(sub=user_id, exp=payload.get("exp"))
+    except JWTError:
+        raise credentials_exception
+    
+    user = db.query(User).filter(User.id == token_data.sub).first()
+    if user is None:
+        raise credentials_exception
+    if not user.is_active:
+        raise HTTPException(status_code=400, detail="Inactive user")
+    return user
\ No newline at end of file
diff --git a/app/api/endpoints/auth.py b/app/api/endpoints/auth.py
new file mode 100644
index 0000000..2c2e71a
--- /dev/null
+++ b/app/api/endpoints/auth.py
@@ -0,0 +1,65 @@
+from datetime import timedelta
+from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi.security import OAuth2PasswordRequestForm
+from sqlalchemy.orm import Session
+from app.core.config import settings
+from app.core.security import create_access_token
+from app.api.deps import get_db
+from app.schemas.user import UserCreate, User
+from app.schemas.token import Token
+from app.crud import crud_user
+from app.core.logging import logger
+
+router = APIRouter()
+
+
+@router.post("/login", response_model=Token)
+async def login(
+    db: Session = Depends(get_db), form_data: OAuth2PasswordRequestForm = Depends()
+):
+    """
+    OAuth2 compatible token login, get an access token for future requests.
+    """
+    user = crud_user.authenticate(
+        db, email=form_data.username, password=form_data.password
+    )
+    if not user:
+        logger.warning(f"Failed login attempt for user: {form_data.username}")
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Incorrect email or password",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+    elif not user.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST, detail="Inactive user"
+        )
+    
+    # Create access token
+    access_token_expires = timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
+    access_token = create_access_token(
+        subject=user.id, expires_delta=access_token_expires
+    )
+    
+    logger.info(f"User {user.id} logged in")
+    return {"access_token": access_token, "token_type": "bearer"}
+
+
+@router.post("/register", response_model=User, status_code=status.HTTP_201_CREATED)
+async def register(user_in: UserCreate, db: Session = Depends(get_db)):
+    """
+    Register a new user.
+    """
+    # Check if the user already exists
+    user = crud_user.get_by_email(db, email=user_in.email)
+    if user:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail="A user with this email already exists",
+        )
+    
+    # Create new user
+    user = crud_user.create(db, obj_in=user_in)
+    logger.info(f"New user registered: {user.id}")
+    
+    return user
\ No newline at end of file
diff --git a/app/api/endpoints/clients.py b/app/api/endpoints/clients.py
new file mode 100644
index 0000000..33253eb
--- /dev/null
+++ b/app/api/endpoints/clients.py
@@ -0,0 +1,101 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from typing import List
+from sqlalchemy.orm import Session
+from app.api.deps import get_db, get_current_user
+from app.models.user import User
+from app.schemas.client import Client, ClientCreate, ClientUpdate
+from app.crud import crud_client
+from app.core.logging import log_activity
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Client])
+async def get_clients(
+    skip: int = 0,
+    limit: int = 100,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Get all clients for the current user.
+    """
+    clients = crud_client.get_multi_by_user(
+        db, user_id=current_user.id, skip=skip, limit=limit
+    )
+    return clients
+
+
+@router.post("/", response_model=Client, status_code=status.HTTP_201_CREATED)
+async def create_client(
+    client_in: ClientCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Create a new client.
+    """
+    client = crud_client.create(db, obj_in=client_in, user_id=current_user.id)
+    log_activity(current_user.id, "create", "client", client.id)
+    return client
+
+
+@router.get("/{client_id}", response_model=Client)
+async def get_client(
+    client_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Get a client by ID.
+    """
+    client = crud_client.get_by_id(db, client_id=client_id, user_id=current_user.id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found",
+        )
+    return client
+
+
+@router.put("/{client_id}", response_model=Client)
+async def update_client(
+    client_id: str,
+    client_in: ClientUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Update a client.
+    """
+    client = crud_client.get_by_id(db, client_id=client_id, user_id=current_user.id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found",
+        )
+    
+    client = crud_client.update(db, db_obj=client, obj_in=client_in)
+    log_activity(current_user.id, "update", "client", client.id)
+    return client
+
+
+@router.delete("/{client_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+async def delete_client(
+    client_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Delete a client.
+    """
+    client = crud_client.get_by_id(db, client_id=client_id, user_id=current_user.id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found",
+        )
+    
+    crud_client.remove(db, client_id=client_id, user_id=current_user.id)
+    log_activity(current_user.id, "delete", "client", client_id)
+    return None
\ No newline at end of file
diff --git a/app/api/endpoints/invoices.py b/app/api/endpoints/invoices.py
new file mode 100644
index 0000000..c656dab
--- /dev/null
+++ b/app/api/endpoints/invoices.py
@@ -0,0 +1,230 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from typing import List
+from fastapi.responses import FileResponse
+from sqlalchemy.orm import Session
+from app.api.deps import get_db, get_current_user
+from app.models.user import User
+from app.schemas.invoice import Invoice, InvoiceCreate, InvoiceUpdate, InvoiceItem, InvoiceItemCreate
+from app.crud import crud_invoice, crud_client
+from app.core.logging import log_activity
+from app.utils.pdf import generate_invoice_pdf
+
+router = APIRouter()
+
+
+@router.get("/", response_model=List[Invoice])
+async def get_invoices(
+    skip: int = 0,
+    limit: int = 100,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Get all invoices for the current user.
+    """
+    invoices = crud_invoice.get_multi_by_user(
+        db, user_id=current_user.id, skip=skip, limit=limit
+    )
+    
+    # Calculate total for each invoice
+    for invoice in invoices:
+        total = sum(item.quantity * item.unit_price for item in invoice.items)
+        invoice.total = total
+    
+    return invoices
+
+
+@router.post("/", response_model=Invoice, status_code=status.HTTP_201_CREATED)
+async def create_invoice(
+    invoice_in: InvoiceCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Create a new invoice.
+    """
+    # Check if client exists and belongs to user
+    client = crud_client.get_by_id(db, client_id=invoice_in.client_id, user_id=current_user.id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found",
+        )
+    
+    invoice = crud_invoice.create(db, obj_in=invoice_in, user_id=current_user.id)
+    log_activity(current_user.id, "create", "invoice", invoice.id)
+    
+    # Calculate total
+    total = sum(item.quantity * item.unit_price for item in invoice.items)
+    invoice.total = total
+    
+    return invoice
+
+
+@router.get("/{invoice_id}", response_model=Invoice)
+async def get_invoice(
+    invoice_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Get an invoice by ID.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    # Calculate total
+    total = sum(item.quantity * item.unit_price for item in invoice.items)
+    invoice.total = total
+    
+    return invoice
+
+
+@router.put("/{invoice_id}", response_model=Invoice)
+async def update_invoice(
+    invoice_id: str,
+    invoice_in: InvoiceUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Update an invoice.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    # If client_id is changed, check if the new client exists and belongs to user
+    if invoice_in.client_id and invoice_in.client_id != invoice.client_id:
+        client = crud_client.get_by_id(db, client_id=invoice_in.client_id, user_id=current_user.id)
+        if not client:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail="Client not found",
+            )
+    
+    invoice = crud_invoice.update(db, db_obj=invoice, obj_in=invoice_in)
+    log_activity(current_user.id, "update", "invoice", invoice.id)
+    
+    # Calculate total
+    total = sum(item.quantity * item.unit_price for item in invoice.items)
+    invoice.total = total
+    
+    return invoice
+
+
+@router.delete("/{invoice_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+async def delete_invoice(
+    invoice_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Delete an invoice.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    crud_invoice.remove(db, invoice_id=invoice_id, user_id=current_user.id)
+    log_activity(current_user.id, "delete", "invoice", invoice_id)
+    return None
+
+
+@router.post("/{invoice_id}/items", response_model=InvoiceItem, status_code=status.HTTP_201_CREATED)
+async def add_invoice_item(
+    invoice_id: str,
+    item_in: InvoiceItemCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Add an item to an invoice.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    item = crud_invoice.add_item(db, invoice_id=invoice_id, user_id=current_user.id, obj_in=item_in)
+    log_activity(current_user.id, "create", "invoice item", item.id)
+    return item
+
+
+@router.delete("/{invoice_id}/items/{item_id}", status_code=status.HTTP_204_NO_CONTENT, response_model=None)
+async def delete_invoice_item(
+    invoice_id: str,
+    item_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Delete an item from an invoice.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    item = crud_invoice.remove_item(db, item_id=item_id, invoice_id=invoice_id, user_id=current_user.id)
+    if not item:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice item not found",
+        )
+    
+    log_activity(current_user.id, "delete", "invoice item", item_id)
+    return None
+
+
+@router.get("/{invoice_id}/pdf")
+async def get_invoice_pdf(
+    invoice_id: str,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Generate and download a PDF for an invoice.
+    """
+    invoice = crud_invoice.get_by_id(db, invoice_id=invoice_id, user_id=current_user.id)
+    if not invoice:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Invoice not found",
+        )
+    
+    client = crud_client.get_by_id(db, client_id=invoice.client_id, user_id=current_user.id)
+    if not client:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Client not found",
+        )
+    
+    try:
+        pdf_path = generate_invoice_pdf(invoice, client)
+        log_activity(current_user.id, "generate", "invoice PDF", invoice_id)
+        
+        return FileResponse(
+            path=pdf_path,
+            filename=f"invoice_{invoice.invoice_number}.pdf",
+            media_type="application/pdf",
+        )
+    except Exception as e:
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail=f"Error generating PDF: {str(e)}",
+        )
\ No newline at end of file
diff --git a/app/api/endpoints/users.py b/app/api/endpoints/users.py
new file mode 100644
index 0000000..e1c0aa5
--- /dev/null
+++ b/app/api/endpoints/users.py
@@ -0,0 +1,31 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.orm import Session
+from app.api.deps import get_db, get_current_user
+from app.models.user import User
+from app.schemas.user import User as UserSchema, UserUpdate
+from app.crud import crud_user
+from app.core.logging import log_activity
+
+router = APIRouter()
+
+
+@router.get("/me", response_model=UserSchema)
+async def read_users_me(current_user: User = Depends(get_current_user)):
+    """
+    Get current user information.
+    """
+    return current_user
+
+
+@router.put("/me", response_model=UserSchema)
+async def update_user_me(
+    user_in: UserUpdate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    """
+    Update current user information.
+    """
+    user = crud_user.update(db, db_obj=current_user, obj_in=user_in)
+    log_activity(user.id, "update", "user profile")
+    return user
\ No newline at end of file
diff --git a/app/api/health.py b/app/api/health.py
new file mode 100644
index 0000000..76ee78b
--- /dev/null
+++ b/app/api/health.py
@@ -0,0 +1,13 @@
+from fastapi import APIRouter, Depends
+from sqlalchemy.ext.asyncio import AsyncSession
+from app.db.session import get_db
+
+router = APIRouter()
+
+
+@router.get("/health", tags=["health"])
+async def health_check(db: AsyncSession = Depends(get_db)):
+    """
+    Health check endpoint to verify the API is running and database connection is working.
+    """
+    return {"status": "ok", "message": "API is running"}
\ No newline at end of file
diff --git a/app/api/routes.py b/app/api/routes.py
new file mode 100644
index 0000000..793dd9d
--- /dev/null
+++ b/app/api/routes.py
@@ -0,0 +1,10 @@
+from fastapi import APIRouter
+from app.api.endpoints import users, clients, invoices, auth
+
+router = APIRouter()
+
+# Include API endpoints
+router.include_router(auth.router, prefix="/auth", tags=["authentication"])
+router.include_router(users.router, prefix="/users", tags=["users"])
+router.include_router(clients.router, prefix="/clients", tags=["clients"])
+router.include_router(invoices.router, prefix="/invoices", tags=["invoices"])
\ No newline at end of file
diff --git a/app/core/config.py b/app/core/config.py
new file mode 100644
index 0000000..5072759
--- /dev/null
+++ b/app/core/config.py
@@ -0,0 +1,28 @@
+from typing import List
+import secrets
+from pydantic import AnyHttpUrl, validator
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    API_V1_STR: str = "/api/v1"
+    # Secret key for JWT token generation
+    SECRET_KEY: str = secrets.token_urlsafe(32)
+    # 60 minutes * 24 hours * 8 days = 8 days
+    ACCESS_TOKEN_EXPIRE_MINUTES: int = 60 * 24 * 8
+    # CORS allowed origins
+    BACKEND_CORS_ORIGINS: List[AnyHttpUrl] = []
+
+    @validator("BACKEND_CORS_ORIGINS", pre=True)
+    def assemble_cors_origins(cls, v: str | List[str]) -> List[str] | str:
+        if isinstance(v, str) and not v.startswith("["):
+            return [i.strip() for i in v.split(",")]
+        elif isinstance(v, (list, str)):
+            return v
+        raise ValueError(v)
+
+    class Config:
+        case_sensitive = True
+
+
+settings = Settings()
\ No newline at end of file
diff --git a/app/core/logging.py b/app/core/logging.py
new file mode 100644
index 0000000..5bdfeef
--- /dev/null
+++ b/app/core/logging.py
@@ -0,0 +1,34 @@
+import sys
+from pathlib import Path
+from loguru import logger
+
+LOG_DIR = Path("/app") / "storage" / "logs"
+LOG_DIR.mkdir(parents=True, exist_ok=True)
+LOG_FILE = LOG_DIR / "app.log"
+
+# Configure loguru logger
+logger.remove()  # Remove default handler
+logger.add(sys.stderr, level="INFO")  # Add stderr handler
+logger.add(
+    LOG_FILE,
+    rotation="10 MB",  # Rotate when file reaches 10 MB
+    retention="30 days",  # Keep logs for 30 days
+    compression="zip",  # Compress rotated logs
+    level="DEBUG",
+)
+
+# Create a function to log user activity
+def log_activity(user_id: str, action: str, object_type: str, object_id: str = None):
+    """
+    Log user activity.
+    
+    Args:
+        user_id: ID of the user performing the action
+        action: The action performed (e.g., "create", "update", "delete")
+        object_type: The type of object the action was performed on (e.g., "invoice", "client")
+        object_id: The ID of the object the action was performed on (optional)
+    """
+    if object_id:
+        logger.info(f"User {user_id} {action}d {object_type} {object_id}")
+    else:
+        logger.info(f"User {user_id} {action}d {object_type}")
\ No newline at end of file
diff --git a/app/core/security.py b/app/core/security.py
new file mode 100644
index 0000000..c2667f2
--- /dev/null
+++ b/app/core/security.py
@@ -0,0 +1,40 @@
+from datetime import datetime, timedelta
+from typing import Any, Union
+from jose import jwt
+from passlib.context import CryptContext
+from app.core.config import settings
+
+pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
+
+ALGORITHM = "HS256"
+
+
+def create_access_token(
+    subject: Union[str, Any], expires_delta: timedelta = None
+) -> str:
+    """
+    Create a JWT access token.
+    """
+    if expires_delta:
+        expire = datetime.utcnow() + expires_delta
+    else:
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+    to_encode = {"exp": expire, "sub": str(subject)}
+    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=ALGORITHM)
+    return encoded_jwt
+
+
+def verify_password(plain_password: str, hashed_password: str) -> bool:
+    """
+    Verify a password against a hash.
+    """
+    return pwd_context.verify(plain_password, hashed_password)
+
+
+def get_password_hash(password: str) -> str:
+    """
+    Hash a password.
+    """
+    return pwd_context.hash(password)
\ No newline at end of file
diff --git a/app/crud/crud_client.py b/app/crud/crud_client.py
new file mode 100644
index 0000000..ca86251
--- /dev/null
+++ b/app/crud/crud_client.py
@@ -0,0 +1,66 @@
+from typing import List, Optional, Dict, Any, Union
+from sqlalchemy.orm import Session
+from app.models.client import Client
+from app.schemas.client import ClientCreate, ClientUpdate
+
+
+def get_by_id(db: Session, client_id: str, user_id: str) -> Optional[Client]:
+    """
+    Get a client by ID, ensuring it belongs to the specified user.
+    """
+    return db.query(Client).filter(
+        Client.id == client_id, Client.user_id == user_id
+    ).first()
+
+
+def get_multi_by_user(
+    db: Session, user_id: str, skip: int = 0, limit: int = 100
+) -> List[Client]:
+    """
+    Get multiple clients for a user.
+    """
+    return db.query(Client).filter(Client.user_id == user_id).offset(skip).limit(limit).all()
+
+
+def create(db: Session, *, obj_in: ClientCreate, user_id: str) -> Client:
+    """
+    Create a new client.
+    """
+    db_obj = Client(
+        **obj_in.dict(),
+        user_id=user_id,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def update(
+    db: Session, *, db_obj: Client, obj_in: Union[ClientUpdate, Dict[str, Any]]
+) -> Client:
+    """
+    Update a client.
+    """
+    update_data = obj_in if isinstance(obj_in, dict) else obj_in.dict(exclude_unset=True)
+    
+    for field, value in update_data.items():
+        if hasattr(db_obj, field) and value is not None:
+            setattr(db_obj, field, value)
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def remove(db: Session, *, client_id: str, user_id: str) -> Optional[Client]:
+    """
+    Delete a client.
+    """
+    client = get_by_id(db, client_id=client_id, user_id=user_id)
+    if not client:
+        return None
+    db.delete(client)
+    db.commit()
+    return client
\ No newline at end of file
diff --git a/app/crud/crud_invoice.py b/app/crud/crud_invoice.py
new file mode 100644
index 0000000..9333872
--- /dev/null
+++ b/app/crud/crud_invoice.py
@@ -0,0 +1,121 @@
+from typing import List, Optional, Dict, Any, Union
+from sqlalchemy.orm import Session
+from app.models.invoice import Invoice, InvoiceItem
+from app.schemas.invoice import InvoiceCreate, InvoiceUpdate, InvoiceItemCreate
+
+
+def get_by_id(db: Session, invoice_id: str, user_id: str) -> Optional[Invoice]:
+    """
+    Get an invoice by ID, ensuring it belongs to the specified user.
+    """
+    return db.query(Invoice).filter(
+        Invoice.id == invoice_id, Invoice.user_id == user_id
+    ).first()
+
+
+def get_multi_by_user(
+    db: Session, user_id: str, skip: int = 0, limit: int = 100
+) -> List[Invoice]:
+    """
+    Get multiple invoices for a user.
+    """
+    return db.query(Invoice).filter(Invoice.user_id == user_id).offset(skip).limit(limit).all()
+
+
+def create(db: Session, *, obj_in: InvoiceCreate, user_id: str) -> Invoice:
+    """
+    Create a new invoice with items.
+    """
+    # Extract items from input
+    items_data = obj_in.items
+    obj_data = obj_in.dict(exclude={"items"})
+    
+    # Create invoice
+    db_obj = Invoice(
+        **obj_data,
+        user_id=user_id,
+    )
+    db.add(db_obj)
+    db.flush()  # Flush to get the invoice ID
+    
+    # Create invoice items
+    for item_data in items_data:
+        db_item = InvoiceItem(
+            **item_data.dict(),
+            invoice_id=db_obj.id,
+        )
+        db.add(db_item)
+    
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def update(
+    db: Session, *, db_obj: Invoice, obj_in: Union[InvoiceUpdate, Dict[str, Any]]
+) -> Invoice:
+    """
+    Update an invoice.
+    """
+    update_data = obj_in if isinstance(obj_in, dict) else obj_in.dict(exclude_unset=True)
+    
+    for field, value in update_data.items():
+        if hasattr(db_obj, field) and value is not None:
+            setattr(db_obj, field, value)
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def remove(db: Session, *, invoice_id: str, user_id: str) -> Optional[Invoice]:
+    """
+    Delete an invoice.
+    """
+    invoice = get_by_id(db, invoice_id=invoice_id, user_id=user_id)
+    if not invoice:
+        return None
+    db.delete(invoice)
+    db.commit()
+    return invoice
+
+
+def add_item(db: Session, *, invoice_id: str, user_id: str, obj_in: InvoiceItemCreate) -> Optional[InvoiceItem]:
+    """
+    Add an item to an invoice.
+    """
+    invoice = get_by_id(db, invoice_id=invoice_id, user_id=user_id)
+    if not invoice:
+        return None
+    
+    db_obj = InvoiceItem(
+        **obj_in.dict(),
+        invoice_id=invoice_id,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def remove_item(db: Session, *, item_id: str, invoice_id: str, user_id: str) -> Optional[InvoiceItem]:
+    """
+    Remove an item from an invoice.
+    """
+    # First check if the invoice belongs to the user
+    invoice = get_by_id(db, invoice_id=invoice_id, user_id=user_id)
+    if not invoice:
+        return None
+    
+    # Then get the item
+    item = db.query(InvoiceItem).filter(
+        InvoiceItem.id == item_id, InvoiceItem.invoice_id == invoice_id
+    ).first()
+    
+    if not item:
+        return None
+    
+    db.delete(item)
+    db.commit()
+    return item
\ No newline at end of file
diff --git a/app/crud/crud_user.py b/app/crud/crud_user.py
new file mode 100644
index 0000000..a5ef45c
--- /dev/null
+++ b/app/crud/crud_user.py
@@ -0,0 +1,68 @@
+from typing import Any, Dict, Optional, Union
+from sqlalchemy.orm import Session
+from app.core.security import get_password_hash, verify_password
+from app.models.user import User
+from app.schemas.user import UserCreate, UserUpdate
+
+
+def get(db: Session, user_id: str) -> Optional[User]:
+    """
+    Get a user by ID.
+    """
+    return db.query(User).filter(User.id == user_id).first()
+
+
+def get_by_email(db: Session, email: str) -> Optional[User]:
+    """
+    Get a user by email.
+    """
+    return db.query(User).filter(User.email == email).first()
+
+
+def create(db: Session, *, obj_in: UserCreate) -> User:
+    """
+    Create a new user.
+    """
+    db_obj = User(
+        email=obj_in.email,
+        hashed_password=get_password_hash(obj_in.password),
+        full_name=obj_in.full_name,
+        is_active=True,
+    )
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def update(
+    db: Session, *, db_obj: User, obj_in: Union[UserUpdate, Dict[str, Any]]
+) -> User:
+    """
+    Update a user.
+    """
+    update_data = obj_in if isinstance(obj_in, dict) else obj_in.dict(exclude_unset=True)
+    if "password" in update_data and update_data["password"]:
+        update_data["hashed_password"] = get_password_hash(update_data["password"])
+        del update_data["password"]
+    
+    for field, value in update_data.items():
+        if hasattr(db_obj, field) and value is not None:
+            setattr(db_obj, field, value)
+    
+    db.add(db_obj)
+    db.commit()
+    db.refresh(db_obj)
+    return db_obj
+
+
+def authenticate(db: Session, *, email: str, password: str) -> Optional[User]:
+    """
+    Authenticate a user by email and password.
+    """
+    user = get_by_email(db, email=email)
+    if not user:
+        return None
+    if not verify_password(password, user.hashed_password):
+        return None
+    return user
\ No newline at end of file
diff --git a/app/db/base.py b/app/db/base.py
new file mode 100644
index 0000000..19a618a
--- /dev/null
+++ b/app/db/base.py
@@ -0,0 +1 @@
+# Import all models here for Alembic to detect them
\ No newline at end of file
diff --git a/app/db/base_class.py b/app/db/base_class.py
new file mode 100644
index 0000000..99441ec
--- /dev/null
+++ b/app/db/base_class.py
@@ -0,0 +1,13 @@
+from typing import Any
+from sqlalchemy.ext.declarative import declared_attr
+from sqlalchemy.orm import DeclarativeBase
+
+
+class Base(DeclarativeBase):
+    id: Any
+    __name__: str
+
+    # Generate __tablename__ automatically
+    @declared_attr.directive
+    def __tablename__(cls) -> str:
+        return cls.__name__.lower()
\ No newline at end of file
diff --git a/app/db/session.py b/app/db/session.py
new file mode 100644
index 0000000..b94ac9a
--- /dev/null
+++ b/app/db/session.py
@@ -0,0 +1,27 @@
+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+# Create storage directory if it doesn't exist
+DB_DIR = Path("/app") / "storage" / "db"
+DB_DIR.mkdir(parents=True, exist_ok=True)
+
+SQLALCHEMY_DATABASE_URL = f"sqlite:///{DB_DIR}/db.sqlite"
+
+engine = create_engine(
+    SQLALCHEMY_DATABASE_URL,
+    connect_args={"check_same_thread": False}
+)
+
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+
+def get_db():
+    """
+    Dependency function that yields db sessions.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/app/models/client.py b/app/models/client.py
new file mode 100644
index 0000000..1e741a2
--- /dev/null
+++ b/app/models/client.py
@@ -0,0 +1,18 @@
+from sqlalchemy import Column, String, ForeignKey
+from sqlalchemy.orm import relationship
+import uuid
+from app.db.base_class import Base
+
+
+class Client(Base):
+    id = Column(String, primary_key=True, index=True, default=lambda: str(uuid.uuid4()))
+    name = Column(String, index=True, nullable=False)
+    email = Column(String, index=True, nullable=False)
+    company = Column(String, nullable=True)
+    address = Column(String, nullable=True)
+    phone = Column(String, nullable=True)
+    user_id = Column(String, ForeignKey("user.id", ondelete="CASCADE"), nullable=False)
+    
+    # Relationships
+    user = relationship("User", back_populates="clients")
+    invoices = relationship("Invoice", back_populates="client", cascade="all, delete-orphan")
\ No newline at end of file
diff --git a/app/models/invoice.py b/app/models/invoice.py
new file mode 100644
index 0000000..988bcf7
--- /dev/null
+++ b/app/models/invoice.py
@@ -0,0 +1,43 @@
+from sqlalchemy import Column, String, Float, ForeignKey, Date, Enum, DateTime, func
+from sqlalchemy.orm import relationship
+import uuid
+import enum
+from datetime import datetime, timedelta
+from app.db.base_class import Base
+
+
+class InvoiceStatus(str, enum.Enum):
+    DRAFT = "draft"
+    SENT = "sent"
+    PAID = "paid"
+    OVERDUE = "overdue"
+    CANCELLED = "cancelled"
+
+
+class Invoice(Base):
+    id = Column(String, primary_key=True, index=True, default=lambda: str(uuid.uuid4()))
+    invoice_number = Column(String, index=True, nullable=False)
+    status = Column(Enum(InvoiceStatus), default=InvoiceStatus.DRAFT, nullable=False)
+    issued_date = Column(Date, default=datetime.utcnow().date, nullable=False)
+    due_date = Column(Date, default=lambda: (datetime.utcnow() + timedelta(days=30)).date(), nullable=False)
+    client_id = Column(String, ForeignKey("client.id", ondelete="CASCADE"), nullable=False)
+    user_id = Column(String, ForeignKey("user.id", ondelete="CASCADE"), nullable=False)
+    notes = Column(String, nullable=True)
+    created_at = Column(DateTime, default=func.now(), nullable=False)
+    updated_at = Column(DateTime, default=func.now(), onupdate=func.now(), nullable=False)
+    
+    # Relationships
+    client = relationship("Client", back_populates="invoices")
+    user = relationship("User", back_populates="invoices")
+    items = relationship("InvoiceItem", back_populates="invoice", cascade="all, delete-orphan")
+
+
+class InvoiceItem(Base):
+    id = Column(String, primary_key=True, index=True, default=lambda: str(uuid.uuid4()))
+    description = Column(String, nullable=False)
+    quantity = Column(Float, nullable=False, default=1.0)
+    unit_price = Column(Float, nullable=False)
+    invoice_id = Column(String, ForeignKey("invoice.id", ondelete="CASCADE"), nullable=False)
+    
+    # Relationships
+    invoice = relationship("Invoice", back_populates="items")
\ No newline at end of file
diff --git a/app/models/user.py b/app/models/user.py
new file mode 100644
index 0000000..50140e6
--- /dev/null
+++ b/app/models/user.py
@@ -0,0 +1,16 @@
+from sqlalchemy import Column, String, Boolean
+from sqlalchemy.orm import relationship
+import uuid
+from app.db.base_class import Base
+
+
+class User(Base):
+    id = Column(String, primary_key=True, index=True, default=lambda: str(uuid.uuid4()))
+    email = Column(String, unique=True, index=True, nullable=False)
+    hashed_password = Column(String, nullable=False)
+    full_name = Column(String, nullable=True)
+    is_active = Column(Boolean, default=True)
+    
+    # Relationships
+    clients = relationship("Client", back_populates="user", cascade="all, delete-orphan")
+    invoices = relationship("Invoice", back_populates="user", cascade="all, delete-orphan")
\ No newline at end of file
diff --git a/app/schemas/client.py b/app/schemas/client.py
new file mode 100644
index 0000000..b21b7bd
--- /dev/null
+++ b/app/schemas/client.py
@@ -0,0 +1,31 @@
+from pydantic import BaseModel, EmailStr
+from typing import Optional
+
+
+class ClientBase(BaseModel):
+    name: str
+    email: EmailStr
+    company: Optional[str] = None
+    address: Optional[str] = None
+    phone: Optional[str] = None
+
+
+class ClientCreate(ClientBase):
+    pass
+
+
+class ClientUpdate(ClientBase):
+    name: Optional[str] = None
+    email: Optional[EmailStr] = None
+
+
+class ClientInDBBase(ClientBase):
+    id: str
+    user_id: str
+
+    class Config:
+        from_attributes = True
+
+
+class Client(ClientInDBBase):
+    pass
\ No newline at end of file
diff --git a/app/schemas/invoice.py b/app/schemas/invoice.py
new file mode 100644
index 0000000..241e4db
--- /dev/null
+++ b/app/schemas/invoice.py
@@ -0,0 +1,69 @@
+from pydantic import BaseModel, Field
+from typing import Optional, List
+from datetime import date
+from app.models.invoice import InvoiceStatus
+
+
+class InvoiceItemBase(BaseModel):
+    description: str
+    quantity: float = Field(..., gt=0)
+    unit_price: float = Field(..., ge=0)
+
+
+class InvoiceItemCreate(InvoiceItemBase):
+    pass
+
+
+class InvoiceItemUpdate(InvoiceItemBase):
+    description: Optional[str] = None
+    quantity: Optional[float] = Field(None, gt=0)
+    unit_price: Optional[float] = Field(None, ge=0)
+
+
+class InvoiceItemInDBBase(InvoiceItemBase):
+    id: str
+    invoice_id: str
+
+    class Config:
+        from_attributes = True
+
+
+class InvoiceItem(InvoiceItemInDBBase):
+    pass
+
+
+class InvoiceBase(BaseModel):
+    invoice_number: str
+    status: InvoiceStatus = InvoiceStatus.DRAFT
+    issued_date: date
+    due_date: date
+    notes: Optional[str] = None
+    client_id: str
+
+
+class InvoiceCreate(InvoiceBase):
+    items: List[InvoiceItemCreate]
+
+
+class InvoiceUpdate(BaseModel):
+    invoice_number: Optional[str] = None
+    status: Optional[InvoiceStatus] = None
+    issued_date: Optional[date] = None
+    due_date: Optional[date] = None
+    notes: Optional[str] = None
+    client_id: Optional[str] = None
+
+
+class InvoiceInDBBase(InvoiceBase):
+    id: str
+    user_id: str
+    created_at: date
+    updated_at: date
+
+    class Config:
+        from_attributes = True
+
+
+class Invoice(InvoiceInDBBase):
+    items: List[InvoiceItem] = []
+    total: float = 0.0
\ No newline at end of file
diff --git a/app/schemas/token.py b/app/schemas/token.py
new file mode 100644
index 0000000..b4de831
--- /dev/null
+++ b/app/schemas/token.py
@@ -0,0 +1,11 @@
+from pydantic import BaseModel
+
+
+class Token(BaseModel):
+    access_token: str
+    token_type: str
+
+
+class TokenPayload(BaseModel):
+    sub: str
+    exp: int
\ No newline at end of file
diff --git a/app/schemas/user.py b/app/schemas/user.py
new file mode 100644
index 0000000..66b1514
--- /dev/null
+++ b/app/schemas/user.py
@@ -0,0 +1,33 @@
+from pydantic import BaseModel, EmailStr, Field
+from typing import Optional
+
+
+class UserBase(BaseModel):
+    email: EmailStr
+    full_name: Optional[str] = None
+
+
+class UserCreate(UserBase):
+    password: str = Field(..., min_length=8)
+
+
+class UserUpdate(BaseModel):
+    email: Optional[EmailStr] = None
+    full_name: Optional[str] = None
+    password: Optional[str] = Field(None, min_length=8)
+
+
+class UserInDBBase(UserBase):
+    id: str
+    is_active: bool
+
+    class Config:
+        from_attributes = True
+
+
+class User(UserInDBBase):
+    pass
+
+
+class UserInDB(UserInDBBase):
+    hashed_password: str
\ No newline at end of file
diff --git a/app/utils/pdf.py b/app/utils/pdf.py
new file mode 100644
index 0000000..d5f8999
--- /dev/null
+++ b/app/utils/pdf.py
@@ -0,0 +1,93 @@
+from pathlib import Path
+from reportlab.lib.pagesizes import letter
+from reportlab.pdfgen import canvas
+from app.models.invoice import Invoice
+from app.models.client import Client
+from datetime import datetime
+
+PDF_DIR = Path("/app") / "storage" / "pdfs"
+PDF_DIR.mkdir(parents=True, exist_ok=True)
+
+
+def generate_invoice_pdf(invoice: Invoice, client: Client) -> str:
+    """
+    Generate a PDF for an invoice and return the path to the PDF file.
+    """
+    # Create a unique filename for the PDF
+    filename = f"invoice_{invoice.invoice_number}_{datetime.now().strftime('%Y%m%d%H%M%S')}.pdf"
+    pdf_path = PDF_DIR / filename
+    
+    # Create a PDF using ReportLab
+    c = canvas.Canvas(str(pdf_path), pagesize=letter)
+    
+    # Add invoice information to the PDF
+    c.setFont("Helvetica-Bold", 18)
+    c.drawString(50, 750, f"Invoice #{invoice.invoice_number}")
+    
+    c.setFont("Helvetica", 12)
+    c.drawString(50, 730, f"Status: {invoice.status}")
+    c.drawString(50, 715, f"Issued Date: {invoice.issued_date}")
+    c.drawString(50, 700, f"Due Date: {invoice.due_date}")
+    
+    # Add client information
+    c.setFont("Helvetica-Bold", 14)
+    c.drawString(50, 670, "Client Information")
+    
+    c.setFont("Helvetica", 12)
+    c.drawString(50, 655, f"Name: {client.name}")
+    c.drawString(50, 640, f"Email: {client.email}")
+    if client.company:
+        c.drawString(50, 625, f"Company: {client.company}")
+    if client.address:
+        c.drawString(50, 610, f"Address: {client.address}")
+    if client.phone:
+        c.drawString(50, 595, f"Phone: {client.phone}")
+    
+    # Add invoice items
+    c.setFont("Helvetica-Bold", 14)
+    c.drawString(50, 560, "Invoice Items")
+    
+    c.setFont("Helvetica", 12)
+    y = 540
+    c.drawString(50, y, "Description")
+    c.drawString(300, y, "Quantity")
+    c.drawString(370, y, "Unit Price")
+    c.drawString(450, y, "Total")
+    
+    y -= 20
+    total = 0
+    
+    for item in invoice.items:
+        item_total = item.quantity * item.unit_price
+        total += item_total
+        
+        c.drawString(50, y, item.description)
+        c.drawString(300, y, str(item.quantity))
+        c.drawString(370, y, f"${item.unit_price:.2f}")
+        c.drawString(450, y, f"${item_total:.2f}")
+        
+        y -= 15
+        
+        # Add a page break if needed
+        if y < 50:
+            c.showPage()
+            c.setFont("Helvetica-Bold", 14)
+            c.drawString(50, 750, "Invoice Items (continued)")
+            c.setFont("Helvetica", 12)
+            y = 730
+    
+    # Add total
+    c.setFont("Helvetica-Bold", 14)
+    c.drawString(370, y - 20, "Total:")
+    c.drawString(450, y - 20, f"${total:.2f}")
+    
+    # Add footer with notes
+    if invoice.notes:
+        c.setFont("Helvetica-Bold", 12)
+        c.drawString(50, 50, "Notes:")
+        c.setFont("Helvetica", 10)
+        c.drawString(50, 35, invoice.notes)
+    
+    c.save()
+    
+    return str(pdf_path)
\ No newline at end of file
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..a78fd13
--- /dev/null
+++ b/main.py
@@ -0,0 +1,30 @@
+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from app.core.config import settings
+from app.api.routes import router as api_router
+from app.api.health import router as health_router
+
+app = FastAPI(
+    title="Freelancer Invoicing API",
+    description="API for managing clients and invoices for freelancers",
+    version="0.1.0",
+)
+
+# Add CORS middleware
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],  # Allow all origins
+    allow_credentials=True,
+    allow_methods=["*"],  # Allow all methods
+    allow_headers=["*"],  # Allow all headers
+)
+
+# Include routers
+app.include_router(health_router)
+app.include_router(api_router, prefix=settings.API_V1_STR)
+
+
+if __name__ == "__main__":
+    import uvicorn
+
+    uvicorn.run("main:app", host="0.0.0.0", port=8000, reload=True)
\ No newline at end of file
diff --git a/migrations/env.py b/migrations/env.py
new file mode 100644
index 0000000..6e1b012
--- /dev/null
+++ b/migrations/env.py
@@ -0,0 +1,80 @@
+from logging.config import fileConfig
+
+from sqlalchemy import engine_from_config
+from sqlalchemy import pool
+
+from alembic import context
+from app.db.base import Base
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+    connectable = engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    with connectable.connect() as connection:
+        is_sqlite = connection.dialect.name == 'sqlite'
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            render_as_batch=is_sqlite,  # Key configuration for SQLite
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()
\ No newline at end of file
diff --git a/migrations/script.py.mako b/migrations/script.py.mako
new file mode 100644
index 0000000..3cf5352
--- /dev/null
+++ b/migrations/script.py.mako
@@ -0,0 +1,26 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}
\ No newline at end of file
diff --git a/migrations/versions/initial_migration.py b/migrations/versions/initial_migration.py
new file mode 100644
index 0000000..4eed221
--- /dev/null
+++ b/migrations/versions/initial_migration.py
@@ -0,0 +1,98 @@
+"""Initial migration
+
+Revision ID: 1a2b3c4d5e6f
+Revises: 
+Create Date: 2023-11-01 00:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = '1a2b3c4d5e6f'
+down_revision: Union[str, None] = None
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Create user table
+    op.create_table(
+        'user',
+        sa.Column('id', sa.String(), nullable=False),
+        sa.Column('email', sa.String(), nullable=False),
+        sa.Column('hashed_password', sa.String(), nullable=False),
+        sa.Column('full_name', sa.String(), nullable=True),
+        sa.Column('is_active', sa.Boolean(), nullable=True),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_user_email'), 'user', ['email'], unique=True)
+    op.create_index(op.f('ix_user_id'), 'user', ['id'], unique=False)
+
+    # Create client table
+    op.create_table(
+        'client',
+        sa.Column('id', sa.String(), nullable=False),
+        sa.Column('name', sa.String(), nullable=False),
+        sa.Column('email', sa.String(), nullable=False),
+        sa.Column('company', sa.String(), nullable=True),
+        sa.Column('address', sa.String(), nullable=True),
+        sa.Column('phone', sa.String(), nullable=True),
+        sa.Column('user_id', sa.String(), nullable=False),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_client_email'), 'client', ['email'], unique=False)
+    op.create_index(op.f('ix_client_id'), 'client', ['id'], unique=False)
+    op.create_index(op.f('ix_client_name'), 'client', ['name'], unique=False)
+
+    # Create invoice table
+    op.create_table(
+        'invoice',
+        sa.Column('id', sa.String(), nullable=False),
+        sa.Column('invoice_number', sa.String(), nullable=False),
+        sa.Column('status', sa.Enum('DRAFT', 'SENT', 'PAID', 'OVERDUE', 'CANCELLED', name='invoicestatus'), nullable=False),
+        sa.Column('issued_date', sa.Date(), nullable=False),
+        sa.Column('due_date', sa.Date(), nullable=False),
+        sa.Column('client_id', sa.String(), nullable=False),
+        sa.Column('user_id', sa.String(), nullable=False),
+        sa.Column('notes', sa.String(), nullable=True),
+        sa.Column('created_at', sa.DateTime(), nullable=False),
+        sa.Column('updated_at', sa.DateTime(), nullable=False),
+        sa.ForeignKeyConstraint(['client_id'], ['client.id'], ondelete='CASCADE'),
+        sa.ForeignKeyConstraint(['user_id'], ['user.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoice_id'), 'invoice', ['id'], unique=False)
+    op.create_index(op.f('ix_invoice_invoice_number'), 'invoice', ['invoice_number'], unique=False)
+
+    # Create invoice_item table
+    op.create_table(
+        'invoiceitem',
+        sa.Column('id', sa.String(), nullable=False),
+        sa.Column('description', sa.String(), nullable=False),
+        sa.Column('quantity', sa.Float(), nullable=False),
+        sa.Column('unit_price', sa.Float(), nullable=False),
+        sa.Column('invoice_id', sa.String(), nullable=False),
+        sa.ForeignKeyConstraint(['invoice_id'], ['invoice.id'], ondelete='CASCADE'),
+        sa.PrimaryKeyConstraint('id')
+    )
+    op.create_index(op.f('ix_invoiceitem_id'), 'invoiceitem', ['id'], unique=False)
+
+
+def downgrade() -> None:
+    op.drop_index(op.f('ix_invoiceitem_id'), table_name='invoiceitem')
+    op.drop_table('invoiceitem')
+    op.drop_index(op.f('ix_invoice_invoice_number'), table_name='invoice')
+    op.drop_index(op.f('ix_invoice_id'), table_name='invoice')
+    op.drop_table('invoice')
+    op.drop_index(op.f('ix_client_name'), table_name='client')
+    op.drop_index(op.f('ix_client_id'), table_name='client')
+    op.drop_index(op.f('ix_client_email'), table_name='client')
+    op.drop_table('client')
+    op.drop_index(op.f('ix_user_id'), table_name='user')
+    op.drop_index(op.f('ix_user_email'), table_name='user')
+    op.drop_table('user')
\ No newline at end of file
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..207ffbb
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,14 @@
+fastapi>=0.104.1
+uvicorn>=0.24.0
+sqlalchemy>=2.0.23
+alembic>=1.12.1
+python-jose[cryptography]>=3.3.0
+passlib[bcrypt]>=1.7.4
+python-multipart>=0.0.6
+pydantic>=2.4.2
+pydantic-settings>=2.0.3
+reportlab>=4.0.7
+loguru>=0.7.2
+ruff>=0.1.3
+python-dateutil>=2.8.2
+email-validator>=2.1.0
\ No newline at end of file