Implement robust notification tracking system
Major improvements:
- Added SQLite database for reliable notification tracking
- Removed problematic is_read filter that was blocking all notifications
- Implemented timestamp-based filtering for continuity between runs
- Added comprehensive debug logging to understand notification flow
- Created recovery tools for missed notifications
- Added queue health monitoring and alerts
- Auto-migration from old JSON format to database
- Periodic cleanup of old notification records
This should significantly improve notification reliability and provide better visibility into what's being processed.