Add quiz clearing and deletion functionality with UI enhancements

This commit introduces the ability to clear quiz results and delete quizzes directly from the backoffice. It includes new routes, controllers, modals for user confirmation, and updates to translations. The `QuizRepository` now supports dedicated methods for clearing results and deleting quizzes along with error handling. Related database migrations and front-end adjustments are also included.

src/Controller/Backoffice/PrepareEliminationController.php

@@ -39,9 +39,10 @@ final class PrepareEliminationController extends AbstractController
             $elimination->updateFromInputBag($request->request);
             $em->flush();
 
-            if (true === $request->request->getBoolean('start')) {
+            if ($request->request->getBoolean('start')) {
                 return $this->redirectToRoute('app_elimination', ['elimination' => $elimination->getId()]);
             }
+
             $this->addFlash('success', 'Elimination updated');
         }