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/views/SettingsView.vue

@@ -27,7 +27,7 @@
       </button>
     </div>
 
-    <!-- Tab strip (copy AdminView pattern verbatim) -->
+    <!-- Tab strip -->
     <div class="flex border-b border-gray-200 mb-6">
       <button
         v-for="tab in tabs"