Add database models and SQLAlchemy setup for todo app

- Created app directory structure with db, models, and schemas modules
- Added SQLAlchemy Base class in app/db/base.py to prevent circular imports
- Implemented database session setup with SQLite configuration
- Created Todo model with id, title, description, completed, created_at, updated_at fields
- Added Pydantic schemas for TodoCreate, TodoUpdate, and TodoResponse
- Added requirements.txt with FastAPI, SQLAlchemy, and other dependencies

app/__init__.py

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+# App package

app/api/__init__.py

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+# API package

app/db/__init__.py

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+# Database package

app/db/base.py

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+from sqlalchemy.ext.declarative import declarative_base
+
+Base = declarative_base()

app/db/session.py

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+from pathlib import Path
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+
+from .base import Base
+
+# Database setup with specified path format
+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)
+
+# Create all tables
+def create_tables():
+    Base.metadata.create_all(bind=engine)
+
+# Dependency to get database session
+def get_db():
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()

app/models/__init__.py

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+# Models package

app/models/todo.py

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+from datetime import datetime
+from sqlalchemy import Column, Integer, String, Text, Boolean, DateTime
+
+from app.db.base import Base
+
+
+class Todo(Base):
+    __tablename__ = "todos"
+
+    id = Column(Integer, primary_key=True, index=True, autoincrement=True)
+    title = Column(String(200), nullable=False, index=True)
+    description = Column(Text, nullable=True)
+    completed = Column(Boolean, default=False, nullable=False)
+    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)

app/schemas/todo.py

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+from datetime import datetime
+from typing import Optional
+from pydantic import BaseModel
+
+
+class TodoBase(BaseModel):
+    title: str
+    description: Optional[str] = None
+
+
+class TodoCreate(TodoBase):
+    pass
+
+
+class TodoUpdate(BaseModel):
+    title: Optional[str] = None
+    description: Optional[str] = None
+    completed: Optional[bool] = None
+
+
+class TodoResponse(TodoBase):
+    id: int
+    completed: bool
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True

main.py

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+from fastapi import FastAPI
+from fastapi.middleware.cors import CORSMiddleware
+from fastapi.responses import JSONResponse
+
+app = FastAPI(
+    title="Todo App API",
+    description="A simple todo application API",
+    version="1.0.0",
+    openapi_url="/openapi.json"
+)
+
+# Configure CORS to allow all origins
+app.add_middleware(
+    CORSMiddleware,
+    allow_origins=["*"],
+    allow_credentials=True,
+    allow_methods=["*"],
+    allow_headers=["*"],
+)
+
+
+@app.get("/")
+async def root():
+    """Base URL endpoint returning project information"""
+    return {
+        "title": "Todo App API",
+        "documentation": "/docs",
+        "redoc": "/redoc",
+        "health": "/health",
+        "openapi": "/openapi.json"
+    }
+
+
+@app.get("/health")
+async def health_check():
+    """Health check endpoint"""
+    return {"status": "healthy", "message": "Todo App API is running"}
+
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run(app, host="0.0.0.0", port=8000)

requirements.txt

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+fastapi==0.104.1
+uvicorn[standard]==0.24.0
+sqlalchemy==2.0.23
+pydantic==2.5.0
+python-multipart==0.0.6
+ruff==0.1.6