fix: add defer tx.Rollback to CreateTipPayment to prevent transaction leak

backend/handlers/payments/handlers.go

@@ -1779,6 +1779,11 @@ func CreateTipPayment(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "internal server error", http.StatusInternalServerError)
 		return
 	}
+	defer func() {
+		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+			slog.Error("failed to rollback transaction", "err", err)
+		}
+	}()
 
 	paymentID, err := service.CreatePaymentRecordTx(r.Context(), tx, record, nil)
 	if err != nil {