Introduced ConnectionManager to support offline-first architecture:
- New internal/db/connection.go with thread-safe connection management
- Lazy connection establishment (5s timeout, 10s cooldown)
- Automatic ping caching (30s interval) to avoid excessive checks
- Updated middleware/offline.go to use ConnectionManager.IsOnline()
- Updated sync/worker.go to use ConnectionManager instead of direct DB
This enables the application to start without MariaDB and gracefully
handle offline/online transitions.
Part of Phase 2.5: Full Offline Mode
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Michael Chus
3d222b7f14