feat: add scheduled sync daemon and TRUNCATE migration mode

- Add sync.py for LAN file sync with atomic writes and mtime-based change detection
- Add watch.py daemon that periodically syncs files and migrates only changed tables
- Add TRUNCATE mode to migrate.py (--truncate flag) to preserve table structure
- Update config.yaml schema with check_interval_minutes and lan_sources
- Update README with new features documentation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -22,6 +22,7 @@ Desktop.ini
 
 # Logs
 *.log
+watch.log
 
 # Environment variables / secrets
 .env