Function cached_album_tracks 

pub(crate) async fn cached_album_tracks(
    db_service: &Arc<RusqliteService>,
    album_id: &str,
) -> Result<Vec<AlbumTrack>, String>

The album’s tracks as the local catalog cache knows them.

Only a fallback for download_album: the cache links a track to its album through items.album_id, which Jellyfin does not populate on every listing endpoint, so this can legitimately return fewer tracks than the album has.

TRACES: UR-018, UR-055 | DR-173