🚧 Add topic explorer

frontend/src/App.tsx

@@ -11,6 +11,7 @@ import { BrokerConfigPage } from "./pages/BrokerConfig";
 import { CertificatesPage } from "./pages/Certificates";
 import { SystemPage } from "./pages/System";
 import { StatusPage } from "./pages/Status";
+import { TopicExplorerPage } from "./pages/TopicExplorer";
 
 // Navigation structure per spec section 57. Entries with a `to` route are
 // implemented; entries without one are planned pages, rendered greyed out
@@ -52,7 +53,7 @@ const NAV_SECTIONS: {
   {
     title: "Tools",
     items: [
-      { label: "Topic Explorer", hint: "Test console (post-MVP)" },
+      { label: "Topic Explorer", to: "/topics" },
       { label: "Connection Test", hint: "Connectivity tester (post-MVP)" },
       { label: "Client Provisioning", hint: "Provisioning wizard (post-MVP)" },
     ],
@@ -254,6 +255,14 @@ export function App() {
           </Protected>
         }
       />
+      <Route
+        path="/topics"
+        element={
+          <Protected>
+            <TopicExplorerPage />
+          </Protected>
+        }
+      />
       <Route path="/" element={<Navigate to="/clients" replace />} />
     </Routes>
   );