Implement complete nested todo tree web app MVP

This commit implements a fully functional self-hosted task decomposition engine with:

Backend (FastAPI + SQLite):
- RESTful API with full CRUD operations for projects and tasks
- Arbitrary-depth hierarchical task structure using self-referencing parent_task_id
- JSON import endpoint for seeding projects from LLM-generated breakdowns
- SQLAlchemy models with proper relationships and cascade deletes
- Status tracking (backlog, in_progress, blocked, done)
- Auto-generated OpenAPI documentation

Frontend (React + Vite + Tailwind):
- Dark cyberpunk theme with orange accents
- Project list page with create/import/delete functionality
- Dual view modes:
  * Tree View: Collapsible hierarchical display with inline editing
  * Kanban Board: Drag-and-drop status management
- Real-time CRUD operations for tasks and subtasks
- JSON import modal with validation
- Responsive design optimized for desktop

Infrastructure:
- Docker setup with multi-stage builds
- docker-compose for orchestration
- Nginx reverse proxy for production frontend
- Named volume for SQLite persistence
- CORS configuration for local development

Documentation:
- Comprehensive README with setup instructions
- Example JSON import file demonstrating nested structure
- API endpoint documentation
- Data model diagrams

backend/Dockerfile

@@ -0,0 +1,16 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+# Install dependencies
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+# Copy application code
+COPY ./app ./app
+
+# Expose port
+EXPOSE 8000
+
+# Run the application
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]