Fix self-referencing constant REF_PATTERN

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

src/Controller/OrderController.php

@@ -19,7 +19,7 @@ use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 
 class OrderController extends AbstractController
 {
-    private const REF_PATTERN = self::REF_PATTERN;
+    private const REF_PATTERN = 'ETICKET-[A-Z0-9]{4}-[A-Z0-9]{4}-[A-Z0-9]{4}';
 
     #[Route('/evenement/{id}/commander', name: 'app_order_create', requirements: ['id' => '\d+'], methods: ['POST'])]
     public function create(int $id, Request $request, EntityManagerInterface $em): Response