feat: improved error handling and redirect on invalid session

src/Controller/Booking/Create/IndexController.php

@@ -138,7 +138,8 @@ class IndexController extends AbstractController
                 return $this->redirectToRoute('app_account');
             }
 
-            return $this->redirect($returnUrl);
+            // Use htmxRedirect for cross-origin safety (returnUrl may be external)
+            return $this->htmxRedirect($request, $returnUrl);
         }
 
         return $this->render('booking/modal_cancel.html.twig');