Ensure all necessary imports and dependencies are included, maintaining consistency with a FastAPI project structure using SQLite and SQLAlchemy.

Here's the `user.py` file for the `app/api/v1/schemas/` directory:

```python
from typing import Optional
from pydantic import BaseModel, EmailStr

# User Schema for Pydantic Model
class UserBase(BaseModel):
    email: EmailStr
    is_active: Optional[bool] = True
    is_superuser: bool = False
    full_name: Optional[str] = None

# Properties to receive via API on creation
class UserCreate(UserBase):
    email: EmailStr
    password: str

# Properties to receive via API on update
class UserUpdate(UserBase):
    password: Optional[str] = None

# Additional properties to return via API
class User(UserBase):
    id: int
    
    class Config:
        orm_mode = True
```

Explanation:

1. The `UserBase` class defines the common properties shared by all user schemas, including `email`, `is_active`, `is_superuser`, and `full_name`.

2. The `UserCreate` class inherits from `UserBase` and adds the `password` field, which is required when creating a new user.

3. The `UserUpdate` class also inherits from `UserBase` and includes an optional `password` field for updating an existing user's password.

4. The `User` class inherits from `UserBase` and adds an `id` field, which is typically the primary key in the database. It also includes the `orm_mode = True` configuration to allow Pydantic to work with SQLAlchemy models.

5. The necessary imports are included at the top of the file, including `typing` for type annotations, `pydantic` for defining the schemas, and `EmailStr` for email validation.

This file defines the Pydantic schemas for the user model in the `blog_app` application, following the FastAPI project structure and using SQLite and SQLAlchemy for database operations.