- Add ReportsSyncQueueModel database model for persistent sync queue storage
- Update ReportsSyncResponseHandler to use database instead of JSON files
- Add transaction safety with rollback support for queue operations
- Implement automatic cleanup of completed items
- Add database indexes for efficient querying
- Create comprehensive test suite for database-based queue (test_reports_sync_db.py)
- Update documentation to reflect database implementation

This change improves performance, data integrity, and scalability of the
reports synchronization feature by migrating from JSON file storage to SQLite database.