feat(torrent): add helper to detect missing files

[s0up4200]

Changes

• Added HasMissingFiles() helper function to detect torrents with missing files on disk

Why

This feature helps identify torrents where the files have been deleted or moved without the torrent client's knowledge. This is particularly useful for:

• Detecting accidental file deletions
• Finding torrents that need rechecking
• Cleanup of torrents where data is no longer available

Example Usage

Add to your config.yaml:

tag:
  - name: missing-files
    mode: full
    update:
      - HasMissingFiles()