get_album_tracks returns rows of any status (needed for re-download
which targets ready+failed but skips downloading). reset_track_for_redownload
clears progress and error so the downloader can restart cleanly.
Also adds OfflineCacheStatus::Pending (serializes/parses as 'pending') so
reset_track_for_redownload has a target state distinct from Queued and
Downloading. The frontend type union (per plan) already includes 'pending'.
Factors out row_to_cached_track_info as a private free function so
get_track, get_all_tracks, and the new get_album_tracks share the same
15-column row decoder.
cc
vicrodh
c47a5558ad