feat(web): router with auth guard, AppShell, login + home views

web/src/App.vue

@@ -1,9 +1,15 @@
 <template>
-  <div class="min-h-screen flex items-center justify-center">
-    <p class="text-lg">Agent Coding Workflow — scaffolding ready.</p>
-  </div>
+  <NConfigProvider :theme="ui.effectiveDark ? darkTheme : null">
+    <NMessageProvider>
+      <NDialogProvider>
+        <RouterView />
+      </NDialogProvider>
+    </NMessageProvider>
+  </NConfigProvider>
 </template>
 
 <script setup lang="ts">
-// 占位组件：I5 接入 router 后改写为 RouterView + NConfigProvider。
+import { NConfigProvider, NMessageProvider, NDialogProvider, darkTheme } from 'naive-ui'
+import { useUIStore } from '@/stores/ui'
+const ui = useUIStore()
 </script>