fix:
- the "Check All Systems" button on the Diagnostics page should now correctly report the database status.
- added comprehensive diagnostic suite to troubleshoot poster manager batch jobs failures
- fix inconsistent authentication in jellyfin_service.py
- standardize all API calls to use header-based auth (X-Emby-Token)
- Remove duplicate API key URL parameters causing HTTP 400 errors
- Fix library item queries to use ItemId instead of Id
- Add enhanced error logging for better debugging
- Add debug scripts for troubleshooting Jellyfin connectivity