perf(前端): 优化页面加载性能和用户体验

- 添加路由预加载功能，使用 requestIdleCallback 在浏览器空闲时预加载
- 配置 Vite manualChunks 分离 vendor 库（vue/ui/chart/i18n/misc）
- 新增 NavigationProgress 导航进度条组件，支持防闪烁和无障碍
- 集成 Vitest 测试框架，添加 40 个单元测试和集成测试
- 支持 prefers-reduced-motion 和暗色模式

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/router/index.ts

@@ -6,6 +6,8 @@
 import { createRouter, createWebHistory, type RouteRecordRaw } from 'vue-router'
 import { useAuthStore } from '@/stores/auth'
 import { useAppStore } from '@/stores/app'
+import { useNavigationLoadingState } from '@/composables/useNavigationLoading'
+import { useRoutePrefetch } from '@/composables/useRoutePrefetch'
 
 /**
  * Route definitions with lazy loading
@@ -326,7 +328,14 @@ const router = createRouter({
  */
 let authInitialized = false
 
+// 初始化导航加载状态和预加载
+const navigationLoading = useNavigationLoadingState()
+const routePrefetch = useRoutePrefetch()
+
 router.beforeEach((to, _from, next) => {
+  // 开始导航加载状态
+  navigationLoading.startNavigation()
+
   const authStore = useAuthStore()
 
   // Restore auth state from localStorage on first navigation (page refresh)
@@ -398,6 +407,17 @@ router.beforeEach((to, _from, next) => {
   next()
 })
 
+/**
+ * Navigation guard: End loading and trigger prefetch
+ */
+router.afterEach((to) => {
+  // 结束导航加载状态
+  navigationLoading.endNavigation()
+
+  // 触发路由预加载（在浏览器空闲时执行）
+  routePrefetch.triggerPrefetch(to)
+})
+
 /**
  * Navigation guard: Error handling
  * Handles dynamic import failures caused by deployment updates