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/vitest.config.ts

@@ -0,0 +1,35 @@
+import { defineConfig, mergeConfig } from 'vitest/config'
+import viteConfig from './vite.config'
+
+export default mergeConfig(
+  viteConfig,
+  defineConfig({
+    test: {
+      globals: true,
+      environment: 'jsdom',
+      include: ['src/**/*.{test,spec}.{js,ts,jsx,tsx}'],
+      exclude: ['node_modules', 'dist'],
+      coverage: {
+        provider: 'v8',
+        reporter: ['text', 'json', 'html'],
+        include: ['src/**/*.{js,ts,vue}'],
+        exclude: [
+          'node_modules',
+          'src/**/*.d.ts',
+          'src/**/*.spec.ts',
+          'src/**/*.test.ts',
+          'src/main.ts'
+        ],
+        thresholds: {
+          global: {
+            statements: 80,
+            branches: 80,
+            functions: 80,
+            lines: 80
+          }
+        }
+      },
+      setupFiles: ['./src/__tests__/setup.ts']
+    }
+  })
+)