feat(subsonic): wire contextual_likes capture/soft-delete into star/unstar

handleStar's track branch calls playevents.CaptureContextualLikeIfPlaying
when the underlying LikeTrack actually inserted a row. handleUnstar
calls SoftDeleteContextualLikes after every track-id unstar. Same
helpers as the api surface — single source of truth.

mediaHandlers struct gains a logger field threaded through Mount.

internal/subsonic/scrobble_test.go

@@ -57,7 +57,7 @@ func testScrobblePool(t *testing.T) (*pgxpool.Pool, dbq.User, dbq.Track) {
 func newScrobbleHandlers(pool *pgxpool.Pool) *mediaHandlers {
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
 	w := playevents.NewWriter(pool, logger, 30*time.Minute, 0.5, 30000)
-	return newMediaHandlers(pool, w)
+	return newMediaHandlers(pool, w, logger)
 }
 
 func TestHandleScrobble_SubmissionFalseInsertsOpenPlayEvent(t *testing.T) {