feat(09-04): delete AdminView + 4 tab files; update tests + router guard test

- git rm AdminView.vue, AdminUsersTab.vue, AdminQuotasTab.vue, AdminAiConfigTab.vue, AuditLogTab.vue
- Migrate tab tests to import from views/admin/Admin*View.vue
- Update router.guard.test.js: replace AdminView mock with AdminLayout + 5 admin view mocks
- Add D-09 redirect test (admin on / → /admin)
- Fix stale api/admin.js JSDoc consumer list
- Fix SettingsView.vue stale AdminView comment reference

frontend/src/api/admin.js

@@ -1,8 +1,8 @@
 /**
  * Admin API — user management, quota, AI config, audit log, daily exports.
  *
- * Consumers: AdminUsersTab.vue, AdminQuotasTab.vue, AdminAiConfigTab.vue,
- *            AuditLogTab.vue, AdminDailyExportsTab.vue
+ * Consumers: AdminUsersView.vue, AdminQuotasView.vue, AdminAiView.vue,
+ *            AdminAuditView.vue
  */
 
 import { request, fetchWithRetry } from './utils.js'