Add brain and chat workspace views

Expand the frontend with brain, graph, and chat workspace updates so the
new backend orchestration and memory features have matching screens.
These changes also wire the new APIs into routing and add focused view
and routing tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/app/layout.vue

@@ -1,6 +1,20 @@
 <script setup lang="ts">
-import { RouterView } from 'vue-router'
+import { watch } from 'vue'
+import { RouterView, useRouter } from 'vue-router'
 import SidebarNav from '@/components/SidebarNav.vue'
+import { useAuthStore } from '@/stores/auth'
+
+const router = useRouter()
+const auth = useAuthStore()
+
+watch(
+  () => auth.isAuthenticated,
+  (isAuthenticated) => {
+    if (!isAuthenticated && router.currentRoute.value.path !== '/login') {
+      void router.replace('/login')
+    }
+  },
+)
 </script>
 
 <template>