feat: add admin tab navigation between subpages

Add AdminLayout wrapper with Tabs component for navigating between
admin sections: User Management, Audit Log, OIDC, Database, OpenSearch.

Nest all /admin/* routes under AdminLayout using React Router's
Outlet pattern so the tab bar persists across admin page navigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/Admin/AdminLayout.tsx

@@ -0,0 +1,26 @@
+import { Outlet, useNavigate, useLocation } from 'react-router';
+import { Tabs } from '@cameleer/design-system';
+
+const ADMIN_TABS = [
+  { label: 'User Management', value: '/admin/rbac' },
+  { label: 'Audit Log', value: '/admin/audit' },
+  { label: 'OIDC', value: '/admin/oidc' },
+  { label: 'Database', value: '/admin/database' },
+  { label: 'OpenSearch', value: '/admin/opensearch' },
+];
+
+export default function AdminLayout() {
+  const navigate = useNavigate();
+  const location = useLocation();
+
+  return (
+    <div>
+      <Tabs
+        tabs={ADMIN_TABS}
+        active={location.pathname}
+        onChange={(path) => navigate(path)}
+      />
+      <Outlet />
+    </div>
+  );
+}

ui/src/router.tsx

@@ -12,6 +12,7 @@ const RoutesMetrics = lazy(() => import('./pages/Routes/RoutesMetrics'));
 const RouteDetail = lazy(() => import('./pages/Routes/RouteDetail'));
 const AgentHealth = lazy(() => import('./pages/AgentHealth/AgentHealth'));
 const AgentInstance = lazy(() => import('./pages/AgentInstance/AgentInstance'));
+const AdminLayout = lazy(() => import('./pages/Admin/AdminLayout'));
 const RbacPage = lazy(() => import('./pages/Admin/RbacPage'));
 const AuditLogPage = lazy(() => import('./pages/Admin/AuditLogPage'));
 const OidcConfigPage = lazy(() => import('./pages/Admin/OidcConfigPage'));
@@ -47,12 +48,18 @@ export const router = createBrowserRouter([
           { path: 'agents', element: <SuspenseWrapper><AgentHealth /></SuspenseWrapper> },
           { path: 'agents/:appId', element: <SuspenseWrapper><AgentHealth /></SuspenseWrapper> },
           { path: 'agents/:appId/:instanceId', element: <SuspenseWrapper><AgentInstance /></SuspenseWrapper> },
-          { path: 'admin', element: <Navigate to="/admin/rbac" replace /> },
-          { path: 'admin/rbac', element: <SuspenseWrapper><RbacPage /></SuspenseWrapper> },
-          { path: 'admin/audit', element: <SuspenseWrapper><AuditLogPage /></SuspenseWrapper> },
-          { path: 'admin/oidc', element: <SuspenseWrapper><OidcConfigPage /></SuspenseWrapper> },
-          { path: 'admin/database', element: <SuspenseWrapper><DatabaseAdminPage /></SuspenseWrapper> },
-          { path: 'admin/opensearch', element: <SuspenseWrapper><OpenSearchAdminPage /></SuspenseWrapper> },
+          {
+            path: 'admin',
+            element: <SuspenseWrapper><AdminLayout /></SuspenseWrapper>,
+            children: [
+              { index: true, element: <Navigate to="/admin/rbac" replace /> },
+              { path: 'rbac', element: <SuspenseWrapper><RbacPage /></SuspenseWrapper> },
+              { path: 'audit', element: <SuspenseWrapper><AuditLogPage /></SuspenseWrapper> },
+              { path: 'oidc', element: <SuspenseWrapper><OidcConfigPage /></SuspenseWrapper> },
+              { path: 'database', element: <SuspenseWrapper><DatabaseAdminPage /></SuspenseWrapper> },
+              { path: 'opensearch', element: <SuspenseWrapper><OpenSearchAdminPage /></SuspenseWrapper> },
+            ],
+          },
           { path: 'api-docs', element: <SuspenseWrapper><SwaggerPage /></SuspenseWrapper> },
         ],
       },