feat: production launch — email audit, team invites, security headers, router fixes

- Fix loyalty & monitoring router bugs (_get_router → named routers)
- Implement team invitation email with send_template + seed templates (en/fr/de)
- Add SecurityHeadersMiddleware (nosniff, HSTS, referrer-policy, permissions-policy)
- Build email audit admin page: service, schemas, API, page route, menu, i18n, HTML, JS
- Clean stale TODO in platform-menu-config.js
- Add 67 tests (unit + integration) covering all new functionality

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

app/modules/messaging/locales/de.json

@@ -59,7 +59,52 @@
         "account_settings": "Kontoeinstellungen",
         "messages": "Nachrichten",
         "notifications": "Benachrichtigungen",
-        "email_templates": "E-Mail-Vorlagen"
+        "email_templates": "E-Mail-Vorlagen",
+        "email_logs": "E-Mail-Protokolle"
+    },
+    "email_logs": {
+        "title": "E-Mail-Protokolle",
+        "subtitle": "Alle über die Plattform gesendeten E-Mails prüfen",
+        "recipient": "Empfänger",
+        "subject": "Betreff",
+        "template": "Vorlage",
+        "status": "Status",
+        "store": "Shop",
+        "date": "Datum",
+        "sent_at": "Gesendet am",
+        "provider": "Anbieter",
+        "from": "Von",
+        "to": "An",
+        "reply_to": "Antwort an",
+        "related_entity": "Verknüpfte Entität",
+        "error_message": "Fehlermeldung",
+        "actions": "Aktionen",
+        "view_detail": "Details anzeigen",
+        "email_detail": "E-Mail-Detail",
+        "html_preview": "HTML-Vorschau",
+        "text_preview": "Text-Vorschau",
+        "metadata": "Metadaten",
+        "content": "Inhalt",
+        "filter_by_recipient": "Nach Empfänger-E-Mail suchen...",
+        "filter_by_status": "Alle Status",
+        "filter_by_template": "Alle Vorlagen",
+        "filter_by_store": "Alle Shops",
+        "date_from": "Von Datum",
+        "date_to": "Bis Datum",
+        "apply_filters": "Anwenden",
+        "reset_filters": "Zurücksetzen",
+        "total_sent": "Gesamt gesendet",
+        "total_failed": "Fehlgeschlagen",
+        "total_pending": "Ausstehend",
+        "total_delivered": "Zugestellt",
+        "no_logs": "Keine E-Mail-Protokolle gefunden",
+        "status_sent": "Gesendet",
+        "status_failed": "Fehlgeschlagen",
+        "status_pending": "Ausstehend",
+        "status_delivered": "Zugestellt",
+        "status_bounced": "Abgewiesen",
+        "status_opened": "Geöffnet",
+        "status_clicked": "Angeklickt"
     },
     "permissions": {
         "view_messages": "Nachrichten anzeigen",