Migrate to Docker Compose with PostgreSQL

- Created docker-compose.yml with 4 services:
  - postgres: PostgreSQL 16 database with persistent volume
  - redis: Redis 7 message broker
  - app: Flask web application (port 5000)
  - celery: Celery worker for async downloads
- Created Dockerfile with Python 3.14, FFmpeg, and uv
- Added psycopg2-binary dependency for PostgreSQL driver
- Updated database.py to use DATABASE_URL environment variable
  - Supports PostgreSQL in production
  - Falls back to SQLite for local development
- Updated celery_app.py to use environment variables:
  - CELERY_BROKER_URL and CELERY_RESULT_BACKEND
- Created .env.example with all configuration variables
- Created .dockerignore to optimize Docker builds
- Updated .gitignore to exclude .env and Docker files
- Updated CLAUDE.md with comprehensive Docker documentation:
  - Quick start with docker-compose commands
  - Environment variable configuration
  - Local development setup instructions
  - Service architecture overview

All services have health checks and automatic restart configured.
Start entire stack with: docker-compose up

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,33 @@
+FROM python:3.14-slim
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y \
+    ffmpeg \
+    postgresql-client \
+    curl \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install uv for faster Python package management
+RUN curl -LsSf https://astral.sh/uv/install.sh | sh
+ENV PATH="/root/.cargo/bin:$PATH"
+
+# Set working directory
+WORKDIR /app
+
+# Copy dependency files
+COPY pyproject.toml uv.lock ./
+
+# Install Python dependencies
+RUN uv sync --frozen
+
+# Copy application code
+COPY . .
+
+# Create downloads directory
+RUN mkdir -p downloads
+
+# Expose Flask port
+EXPOSE 5000
+
+# Default command (can be overridden in docker-compose)
+CMD ["flask", "--app", "main", "run", "--host=0.0.0.0"]