Backend validation rejected 'playCount' as unknown column ID, silently
preventing it from being enabled or persisted. Added ColPlayCount to
the tracklist package's constant list and AllColumnIDs slice.
Backend:
- GetAllTracksWithFullMetadata queries now select play_count and last_played
- mapTrackRow accepts and passes through PlayCount/LastPlayed
- PlayCount + LastPlayed added to library.Track struct
- sqlcgen Row types updated with new fields
Frontend:
- PlayCount + LastPlayed added to library.Track TypeScript model
- 'Plays' column added to track-list column definitions (60px, right-aligned, sortable)
Queries without play data (search, genre, album) pass 0/empty defaults.