fix: address code review issues

- Rename `read` column to `is_read` (PostgreSQL reserved word)
- Wrap navbar + modal in parent div for Stimulus controller scope
- Set temporary filePath before first flush in ImportController
- Use RETURNING clause for atomic incrementProcessedBatches
- Return proper empty 204 response in NotificationController

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Controller/ImportController.php

@@ -46,6 +46,7 @@ class ImportController extends AbstractController
 
         $import = new Import();
         $import->setUser($user);
+        $import->setFilePath('pending');
 
         $em->persist($import);
         $em->flush();

src/Controller/NotificationController.php

@@ -37,13 +37,13 @@ class NotificationController extends AbstractController
 
     #[Route('/api/notifications/read', methods: ['POST'])]
     #[IsGranted('ROLE_USER')]
-    public function markRead(NotificationRepository $notificationRepository): JsonResponse
+    public function markRead(NotificationRepository $notificationRepository): Response
     {
         /** @var User $user */
         $user = $this->getUser();
 
         $notificationRepository->markAllReadForUser($user);
 
-        return $this->json(null, Response::HTTP_NO_CONTENT);
+        return new Response('', Response::HTTP_NO_CONTENT);
     }
 }