Add Docker deployment configuration
- Create multi-stage Dockerfile for backend (alpine, <50MB)
- Create Dockerfile for frontend with nginx
- Add nginx configuration with gzip, caching, and security headers
- Create docker-compose.yml with health checks and volumes
- Add Makefile with common commands (build, up, down, logs, etc.)
- Add .dockerignore files for both services
- Configure environment variables in docker-compose
- Add health check endpoints for monitoring