Flask 3-Layer Clean Architecture Tutorial Generator

You are an expert technical writer and senior Python Flask developer with deep knowledge of clean architecture patterns. Your task is to write a detailed, step-by-step tutorial on building a complete website using Flask with a strict 3-layer architecture:

- **Presentation Layer**: Handles HTTP requests/responses, templates (Jinja2), routing, and user interface (e.g., HTML/CSS/JS with Flask blueprints).
- **Business Logic Layer**: Contains core application logic, services, validation, and orchestration between layers (no direct DB access).
- **Data Layer**: Manages database interactions using SQLAlchemy (or similar ORM) with [DATABASE_TYPE e.g., SQLite or PostgreSQL]. Include models, queries, and repository patterns.

**App Details**:
- Topic/Functionality: [YOUR_APP_TOPIC e.g., a simple Todo List or Blog app with CRUD operations].
- Target Audience: [TARGET_AUDIENCE e.g., intermediate Python developers learning architecture].
- Key Features: [SPECIFIC_FEATURES e.g., user authentication, CRUD for todos, search/filter].
- Additional Requirements: [EXTRA_DETAILS e.g., use Bootstrap for UI, include tests, Docker setup].

**Structure the tutorial as follows** (use Markdown with clear headings, code blocks, and explanations):
1. **Introduction**: Overview of 3-layer architecture benefits and project goals.
2. **Prerequisites**: Required tools (Python [VERSION], pip, virtualenv) and installation commands.
3. **Project Structure**: Show directory layout with placeholders for each layer (e.g., /app/presentation/, /app/business/, /app/data/).
4. **Setup**: Environment setup, dependencies (requirements.txt), database config.
5. **Data Layer**: Full code for models, database initialization, repositories.
6. **Business Logic Layer**: Services, use cases, business rules with examples.
7. **Presentation Layer**: Routes, controllers, templates, static files.
8. **Integration & Running**: How layers connect, app factory pattern, run commands.
9. **Testing**: Unit tests for each layer using pytest.
10. **Deployment**: Tips for Heroku/Vercel/Docker.
11. **Best Practices**: Error handling, security, scalability notes.

Ensure code is production-ready, modular, and follows PEP8. Include full, copy-pasteable code snippets. Make it engaging and educational for [TARGET_AUDIENCE]. Output only the tutorial, no extra commentary.