feat: allow watch progress restore via backup file

[arabcoders]

This pull request introduces several documentation improvements, backend-specific guidance, and enhancements to the backend restore process. The most significant changes include the creation of a comprehensive backend limitations guide, updates to documentation and UI to reference this new guide, and new features and reliability improvements for the backend restore command.

Documentation and User Guidance Updates:

• Added a new guides/backend-limitations.md file that details requirements and known limitations for each supported backend (Plex, Jellyfin, Emby), including webhook behaviors and troubleshooting tips.
• Updated references in documentation and frontend UI to point to the new backend limitations guide instead of duplicating or scattering backend-specific advice:
  • Changed FAQ and webhook docs to reference the backend limitations guide. [1] [2]
  • Added a "Backend limitations" entry to the help menu and a prominent link in the backend add UI. [1] [2]
  • Removed duplicated webhook backend limitations from webhooks.md in favor of the new guide. [1] [2]

Backend Restore Command Enhancements:

• Added a --restore-watch-progress option to the backend restore command, enabling restoration of watch progress in addition to play state. The process now separately tracks and logs stats for play state, change state, and progress requests, and provides improved error handling and reporting. [1] [2] [3] [4] [5]
• Improved reliability by resetting the request queue at appropriate stages and adding a try/catch/finally block to ensure cleanup and error logging on failure. [1] [2]

Other Improvements:

• Updated the default file logger level in config.php from Warning to Error for less noisy logging.
• Enhanced backup command to handle empty backups more gracefully, deleting empty files and logging a warning.
• Fixed logging in ProcessProfileEvent listener to use the correct writer function for error and notice messages.
• Updated import restore mapper to handle progress metadata correctly when loading data.