Fix monitor state: never downgrade on upsert, explicitly set monitored on MonitorAlbum

internal/database/album_repository.go

@@ -48,6 +48,7 @@ func (r *AlbumRepository) Create(ctx context.Context, a *Album) error {
 		   cover_url = EXCLUDED.cover_url,
 		   monitor_state = CASE
 		     WHEN albums.monitor_state = 'excluded' THEN albums.monitor_state
+		     WHEN albums.monitor_state = 'monitored' THEN albums.monitor_state
 		     ELSE EXCLUDED.monitor_state
 		   END,
 		   updated_at = NOW()`,