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/db/dbq/likes.sql.go

@@ -76,7 +76,7 @@ func (q *Queries) LikeArtist(ctx context.Context, arg LikeArtistParams) error {
 	return err
 }
 
-const likeTrack = `-- name: LikeTrack :exec
+const likeTrack = `-- name: LikeTrack :execrows
 INSERT INTO general_likes (user_id, track_id)
 VALUES ($1, $2)
 ON CONFLICT (user_id, track_id) DO NOTHING
@@ -87,9 +87,12 @@ type LikeTrackParams struct {
 	TrackID pgtype.UUID
 }
 
-func (q *Queries) LikeTrack(ctx context.Context, arg LikeTrackParams) error {
-	_, err := q.db.Exec(ctx, likeTrack, arg.UserID, arg.TrackID)
-	return err
+func (q *Queries) LikeTrack(ctx context.Context, arg LikeTrackParams) (int64, error) {
+	result, err := q.db.Exec(ctx, likeTrack, arg.UserID, arg.TrackID)
+	if err != nil {
+		return 0, err
+	}
+	return result.RowsAffected(), nil
 }
 
 const listLikedAlbumIDs = `-- name: ListLikedAlbumIDs :many