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/en.json

@@ -76,6 +76,54 @@
         "account_settings": "Account Settings",
         "messages": "Messages",
         "notifications": "Notifications",
-        "email_templates": "Email Templates"
+        "email_templates": "Email Templates",
+        "email_logs": "Email Logs"
+    },
+    "email_logs": {
+        "title": "Email Logs",
+        "subtitle": "Audit all emails sent through the platform",
+        "recipient": "Recipient",
+        "subject": "Subject",
+        "template": "Template",
+        "status": "Status",
+        "store": "Store",
+        "date": "Date",
+        "sent_at": "Sent At",
+        "provider": "Provider",
+        "from": "From",
+        "to": "To",
+        "reply_to": "Reply To",
+        "related_entity": "Related Entity",
+        "error_message": "Error Message",
+        "retry_count": "Retry Count",
+        "actions": "Actions",
+        "view_detail": "View Detail",
+        "email_detail": "Email Detail",
+        "html_preview": "HTML Preview",
+        "text_preview": "Text Preview",
+        "metadata": "Metadata",
+        "content": "Content",
+        "status_timeline": "Status Timeline",
+        "filter_by_recipient": "Search by recipient email...",
+        "filter_by_status": "All statuses",
+        "filter_by_template": "All templates",
+        "filter_by_store": "All stores",
+        "date_from": "From date",
+        "date_to": "To date",
+        "apply_filters": "Apply",
+        "reset_filters": "Reset",
+        "total_sent": "Total Sent",
+        "total_failed": "Failed",
+        "total_pending": "Pending",
+        "total_delivered": "Delivered",
+        "no_logs": "No email logs found",
+        "status_sent": "Sent",
+        "status_failed": "Failed",
+        "status_pending": "Pending",
+        "status_delivered": "Delivered",
+        "status_bounced": "Bounced",
+        "status_opened": "Opened",
+        "status_clicked": "Clicked",
+        "retention_note": "Email body content is retained for 90 days. Metadata is kept indefinitely."
     }
 }