fix: translate remaining NL/FR interface gaps

Role names, audit/scenario labels, and status text were previously either
left in English or only partially translated:
- auth.json/demo.json role labels actually translated (not just labelled
  as translated): Operationsmanager/Verhuurmedewerker,
  Responsable des operations/Collaborateur de location.
- "Audit trail" -> Auditgeschiedenis/Piste d'audit (title, column header,
  and every mid-sentence occurrence across demo.json, quality.json,
  returns.json -- these embedded leaks were previously invisible to the
  whole-string identity check).
- "Open" (status) -> Openstaand, "Recent" -> Recentste,
  "Start scenario" -> Scenario starten / Demarrer le scenario.

Matching Playwright spec text updated in the same commit so the suite
never regresses through a broken intermediate state.

frontend/src/i18n/locales/fr-BE/integrations.json

@@ -41,7 +41,7 @@
     "statusSucceeded": "Réussi",
     "statusFailed": "Échoué",
     "unavailable": "Les tâches d'automatisation sont actuellement indisponibles.",
-    "managerOnly": "L'automatisation est visible uniquement pour les Operations Managers.",
+    "managerOnly": "L'automatisation est visible uniquement pour les Responsables des opérations.",
     "loading": "Chargement des tâches d'automatisation…",
     "empty": "Aucune tâche d'automatisation ne correspond à ce filtre.",
     "count": "{{count}} événements de workflow",