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/monitoring/definition.py

@@ -140,7 +140,7 @@ def get_monitoring_module_with_routers() -> ModuleDefinition:
     This function attaches the routers lazily to avoid circular imports
     during module initialization.
     """
-    monitoring_module.router = _get_router()
+    monitoring_module.admin_router = _get_admin_router()
     return monitoring_module