fix: correct lock guards, flush batching, and clearQuiz atomicity in question bank

- syncUsagesAfterEdit: use isLocked() instead of !isFinalized() to avoid
  syncing quizzes with started candidates (would have destroyed GivenAnswer records)
- syncToQuiz action: use isLocked() instead of hasStartedCandidates() to block
  syncing into finalized quizzes that have no started candidates
- QuestionBankService::syncToQuiz: remove internal flush(); callers now
  flush once (syncUsagesAfterEdit after the loop, syncToQuiz action after the call)
- QuizRepository::clearQuiz: delete BankQuestionUsage rows and reset
  finalized_at inside the transaction (previously orphaned usages blocked
  bank question reassignment; finalizedAt reset was a separate non-atomic flush)
- QuizController::finalizeQuiz: add flash when quiz is already finalized
- QuestionBankController::delete: block deletion when any usage references a locked quiz
- BankQuestion::__toString: remove dead null-coalescing on non-nullable string
- SeasonController::addBlankQuiz: align form field with UploadQuizFormType
  (add translation_domain: false, use translator for label)

src/Controller/Backoffice/QuestionBankController.php

@@ -150,6 +150,15 @@ class QuestionBankController extends AbstractController
     {
         $this->assertSameSeason($season, $bankQuestion->season);
 
+        $hasLockedUsages = $bankQuestion->usages->exists(
+            static fn (int $key, BankQuestionUsage $usage): bool => $usage->quiz->isLocked(),
+        );
+        if ($hasLockedUsages) {
+            $this->addFlash(FlashType::Danger, $this->translator->trans('This question cannot be deleted because it is used in a locked or active quiz'));
+
+            return $this->redirectToRoute('tvdt_backoffice_question_bank', ['seasonCode' => $season->seasonCode]);
+        }
+
         $this->em->remove($bankQuestion);
         $this->em->flush();
 
@@ -299,13 +308,14 @@ class QuestionBankController extends AbstractController
             throw new NotFoundHttpException();
         }
 
-        if ($usage->quiz->hasStartedCandidates()) {
+        if ($usage->quiz->isLocked()) {
-            $this->addFlash(FlashType::Danger, $this->translator->trans('This quiz has already been filled in and can no longer be altered'));
+            $this->addFlash(FlashType::Danger, $this->translator->trans('This quiz can no longer be altered'));
 
             return $this->redirectToRoute('tvdt_backoffice_question_bank', ['seasonCode' => $season->seasonCode]);
         }
 
         $this->questionBankService->syncToQuiz($bankQuestion, $usage);
+        $this->em->flush();
         $this->addFlash(FlashType::Success, $this->translator->trans('Question synced to quiz %quiz%', ['%quiz%' => $usage->quiz->name]));
 
         return $this->redirectToRoute('tvdt_backoffice_question_bank', ['seasonCode' => $season->seasonCode]);
@@ -329,14 +339,20 @@ class QuestionBankController extends AbstractController
     private function syncUsagesAfterEdit(BankQuestion $bankQuestion): void
     {
         $pendingNames = [];
+        $synced = false;
         foreach ($bankQuestion->usages as $usage) {
-            if (!$usage->quiz->isFinalized()) {
+            if (!$usage->quiz->isLocked()) {
                 $this->questionBankService->syncToQuiz($bankQuestion, $usage);
-            } elseif (!$usage->quiz->hasStartedCandidates()) {
+                $synced = true;
+            } else {
                 $pendingNames[] = $usage->quiz->name;
             }
         }
 
+        if ($synced) {
+            $this->em->flush();
+        }
+
         if ([] !== $pendingNames) {
             $this->addFlash(
                 FlashType::Warning,

src/Controller/Backoffice/QuizController.php

@@ -297,8 +297,6 @@ class QuizController extends AbstractController
     {
         try {
             $this->quizRepository->clearQuiz($quiz);
-            $quiz->finalizedAt = null;
-            $this->em->flush();
             $this->addFlash(FlashType::Success, $this->translator->trans('Quiz cleared and no longer finalized'));
         } catch (ErrorClearingQuizException) {
             $this->addFlash(FlashType::Danger, $this->translator->trans('Error clearing quiz'));
@@ -323,6 +321,8 @@ class QuizController extends AbstractController
             $quiz->finalizedAt = new DateTimeImmutable();
             $this->em->flush();
             $this->addFlash(FlashType::Success, $this->translator->trans('Quiz finalized'));
+        } else {
+            $this->addFlash(FlashType::Warning, $this->translator->trans('The quiz is already finalized'));
         }
 
         return $this->redirectToRoute('tvdt_backoffice_quiz', ['seasonCode' => $quiz->season->seasonCode, 'quiz' => $quiz->id]);

src/Controller/Backoffice/SeasonController.php

@@ -161,7 +161,7 @@ class SeasonController extends AbstractController
     public function addBlankQuiz(Request $request, Season $season): Response
     {
         $form = $this->createFormBuilder(new Quiz())
-            ->add('name', TextType::class, ['label' => 'Quiz name'])
+            ->add('name', TextType::class, ['label' => $this->translator->trans('Quiz name'), 'translation_domain' => false])
             ->add('save', SubmitType::class, ['label' => 'Create'])
             ->getForm();
 

src/Entity/BankQuestion.php

@@ -131,6 +131,6 @@ class BankQuestion implements \Stringable
 
     public function __toString(): string
     {
-        return $this->question ?? '';
+        return $this->question;
     }
 }

src/Repository/QuizRepository.php

@@ -72,6 +72,20 @@ class QuizRepository extends ServiceEntityRepository
                 DQL)
                 ->setParameter('quiz', $quiz)
                 ->execute();
+
+            $em->createQuery(<<<DQL
+                delete from Tvdt\Entity\BankQuestionUsage bqu
+                where bqu.quiz = :quiz
+                DQL)
+                ->setParameter('quiz', $quiz)
+                ->execute();
+
+            $em->createQuery(<<<DQL
+                update Tvdt\Entity\Quiz q set q.finalizedAt = null
+                where q = :quiz
+                DQL)
+                ->setParameter('quiz', $quiz)
+                ->execute();
         }
         // @codeCoverageIgnoreStart
         catch (\Throwable $throwable) {

src/Service/QuestionBankService.php

@@ -97,8 +97,6 @@ final readonly class QuestionBankService
             $answer = $this->objectMapper->map($bankAnswer, Answer::class);
             $question->addAnswer($answer);
         }
-
-        $this->entityManager->flush();
     }
 
     /** Remove the quiz copy created by this usage and delete the usage record. */