- Add dj-database-url package for parsing DATABASE_URL
- Replace hardcoded PostgreSQL config with DATABASE_URL environment variable
- Add connection pooling with conn_max_age and health checks
- Fallback to SQLite for local development when DATABASE_URL is not set
- Remove obsolete production config comments
- Update requirements.txt with new dependency
This change improves deployment flexibility by supporting standard DATABASE_URL format commonly used in cloud platforms (Heroku, Railway, etc.) while maintaining backward compatibility with local development using SQLite.
