前端: 浅色模式 + 系统自动主题

- 引入语义化 CSS 变量令牌(bg/surface/edge/ink/muted/accent 等), data-theme 三态切换
- theme store(localStorage + 系统偏好跟随), 首屏内联脚本防主题闪烁
- ThemeToggle 组件(浅色/深色/跟随系统) 置于导航与控制台顶栏
- 全量替换硬编码 zinc/emerald/red 类为令牌, 图表基线/状态色随主题适配
- 浅色对比度校准(accent/err/warn 深浅各一套)

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

web/src/main.ts

@@ -2,12 +2,12 @@ import { createApp } from 'vue'
 import { createPinia } from 'pinia'
 import App from './App.vue'
 import { router } from './router'
+import { useThemeStore } from './stores/theme'
 import './style.css'
 
-// 深色优先（MVP 固定深色，后续加亮色切换）
-document.documentElement.classList.add('dark')
-
 const app = createApp(App)
-app.use(createPinia())
+const pinia = createPinia()
+app.use(pinia)
+useThemeStore(pinia).init()
 app.use(router)
 app.mount('#app')