RemoveTrack handles both Lidarr-managed (delegates to existing
lidarrquarantine.DeleteViaLidarr) and non-Lidarr (direct os.Remove)
file deletion, then runs the cascade album-if-empty / artist-if-empty
DB cleanup in a single transaction. Lidarr errors propagate as typed
errors so the API layer can map them to the existing wire codes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
