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>

templates/_navbar.html.twig

@@ -1,4 +1,5 @@
 {% if app.user %}
+<div data-controller="import-modal">
 <nav class="navbar" data-controller="notifications">
     <div class="navbar-left">
         <a href="{{ path('app_homepage') }}" class="navbar-brand">Actorle</a>
@@ -38,7 +39,7 @@
 </nav>
 
 {# Import Modal #}
-<div class="modal-overlay" data-controller="import-modal" data-import-modal-target="overlay" hidden>
+<div class="modal-overlay" data-import-modal-target="overlay" hidden>
     <div class="modal">
         <div class="modal-header">
             <h2>Importer ses films</h2>
@@ -56,4 +57,5 @@
         </div>
     </div>
 </div>
+</div>
 {% endif %}