- Store client key in SQLite database instead of environment variable
- Add database migration from CLIENT_KEY environment variable to preserve existing keys
- Add admin UI with tabbed interface (Configuration and QR Code tabs)
- Implement QR code generation containing server config (address, port, key) for Android app
- Add functionality to regenerate client key with warning dialog
- Add buttons to download QR code as PNG and copy QR image to clipboard
- Add manual input fields for server address and port configuration
- Update requirements.txt with pyotp and qrcode dependencies
- Replace JSON file storage with SQLite database for improved concurrency and data integrity
- Implement repository pattern with dedicated model layer (admin_model, file_model, chunk_model)
- Add database.py with automatic migration from existing JSON files
- Enable WAL mode for thread-safe concurrent access across Gunicorn workers
- Store database files in dedicated db/ folder
- Update controllers to use model layer instead of direct JSON access
- Add admin authentication system with TOTP 2FA support
