Fix undefined $email variable in createInvitation, use $order->getEmail()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Controller/AccountController.php

@@ -772,7 +772,7 @@ class AccountController extends AbstractController
 
         $billetOrderService->generateAndSendTickets($order);
 
-        $this->addFlash('success', 'Invitation envoyee a '.$email.'.');
+        $this->addFlash('success', 'Invitation envoyee a '.$order->getEmail().'.');
 
         return $this->redirectToRoute('app_account_edit_event', ['id' => $event->getId(), 'tab' => 'invitations']);
     }