feat: Phase 3 - API layer + Pinia stores + app integration

- HTTP client (axios interceptors, token mgmt, typed APIs)
- Pinia stores: token, user (login/logout), app (dark mode, sidebar)
- globalConfig TS types + Window augmentation
- Vue Router (hash history, auth guard)
- Login/Home/Mine pages (Vant UI)
- Vant integration + globalConfig dev script
- Build passes (vue-tsc + vite)

src/App.vue

@@ -1,7 +1,22 @@
 <script setup lang="ts">
-import HelloWorld from './components/HelloWorld.vue'
+/**
+ * 应用根组件
+ *
+ * 使用 Vant ConfigProvider 包裹路由视图，
+ * 提供全局主题配置和路由出口。
+ */
 </script>
 
 <template>
-  <HelloWorld />
+  <van-config-provider>
+    <router-view />
+  </van-config-provider>
 </template>
+
+<style>
+/* App-level 全局样式调整 */
+#app {
+  width: 100%;
+  min-height: 100vh;
+}
+</style>