Fix: Handle matches with NULL start_time in cleanup logic

- Updated _cleanup_old_incomplete_matches() to also check matches with NULL start_time using created_at as fallback
- Updated _get_yesterday_incomplete_matches() to also check matches with NULL start_time using created_at as fallback
- Added detailed debug logging to help diagnose date/time issues
- This fixes the issue where matches from old fixtures were not being detected because their start_time was NULL or recently synced