feat(admin): add model config CRUD and platform bridge pages

- Backend: ModelConfigStore with Provider/Model/Routing CRUD
- Backend: /api/v1/admin/models/config endpoints
- Frontend: ModelsPage with 3-tab editor (providers/models/routing)
- Frontend: BridgePage showing adapter status + group chat rules
- Admin nav expanded to 9 items

frontend/web/src/App.tsx

@@ -10,6 +10,8 @@ import PluginsPage from './pages/admin/PluginsPage'
 import MemoryPage from './pages/admin/MemoryPage'
 import LLMCallsPage from './pages/admin/LLMCallsPage'
 import SystemPage from './pages/admin/SystemPage'
+import ModelsPage from './pages/admin/ModelsPage'
+import BridgePage from './pages/admin/BridgePage'
 import LoginPage from './pages/LoginPage'
 
 export default function App() {
@@ -38,6 +40,8 @@ export default function App() {
           <Route path="plugins" element={<PluginsPage />} />
           <Route path="memory" element={<MemoryPage />} />
           <Route path="llm-calls" element={<LLMCallsPage />} />
+          <Route path="models" element={<ModelsPage />} />
+          <Route path="bridge" element={<BridgePage />} />
           <Route path="system" element={<SystemPage />} />
         </Route>
       </Routes>