feat(db): add session-vector capture queries; LikeTrack returns row count

ListRecentSessionTracks + UpdatePlayEventVector for the vector capture
path inside RecordPlayStarted. LikeTrack switches to :execrows so the
contextual-likes capture can detect insert vs already-exists. Existing
callers updated to ignore the count for now; later tasks consume it.

internal/subsonic/star.go

@@ -38,7 +38,7 @@ func (m *mediaHandlers) handleStar(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	if trackID.Valid {
-		if err := q.LikeTrack(r.Context(), dbq.LikeTrackParams{UserID: user.ID, TrackID: trackID}); err != nil {
+		if _, err := q.LikeTrack(r.Context(), dbq.LikeTrackParams{UserID: user.ID, TrackID: trackID}); err != nil {
 			WriteFail(w, r, ErrGeneric, "Could not star track")
 			return
 		}