Adds webhook-based update system that allows triggering updates
directly from the mc-webui menu. Includes:
- Webhook server (updater.py) on port 5050
- Systemd service and install script
- API proxy endpoints for container-to-host communication
- Update modal with progress tracking and auto-reload
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
