fix(api) : fix mark-all-read using undefined executeStatement on DQL query

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

src/Repository/NotificationRepository.php

@@ -40,7 +40,7 @@ class NotificationRepository extends ServiceEntityRepository
             ->andWhere('n.isRead = false')
             ->setParameter('user', $user)
             ->getQuery()
-            ->executeStatement()
+            ->execute()
         ;
     }
 }