feat(web): 整体替换 UI 框架为 Ant Design 6 并接入自定义主题

以 antd ConfigProvider + antd-style 承载 zinc 风格自定义主题（明暗双套 token），
button/input/select/notification 用 createStyles 定制；三态主题经
darkAlgorithm 无刷新切换；use-toast 改基于 antd notification；
移除 shadcn/ui 组件目录与 radix 依赖；样式桥接层保证排版与多端布局不变。

web/src/App.tsx

@@ -1,7 +1,11 @@
-import { lazy, Suspense } from 'react'
-import { Navigate, Route, Routes } from 'react-router'
+import { lazy, Suspense, useEffect, useState } from 'react'
 import type { ReactNode } from 'react'
+import { Navigate, Route, Routes } from 'react-router'
+import { App as AntdApp, ConfigProvider } from 'antd'
+import zhCN from 'antd/locale/zh_CN'
 import { useAuth } from './lib/auth'
+import { useTheme } from './lib/theme'
+import useShadcnTheme from './theme/shadcnTheme'
 import { BlogLayout, AdminLayout } from './components/Layout'
 import Home from './pages/Home'
 import TagPage from './pages/TagPage'
@@ -16,6 +20,27 @@ import NotFound from './pages/NotFound'
 const Note = lazy(() => import('./pages/Note'))
 const AdminEdit = lazy(() => import('./pages/AdminEdit'))
 
+// antd ConfigProvider：跟随应用三态主题切换 light/dark 算法（system 监听系统变化）
+function AntdProvider({ children }: { children: ReactNode }) {
+  const { mode } = useTheme()
+  const [systemDark, setSystemDark] = useState(
+    () => window.matchMedia('(prefers-color-scheme: dark)').matches,
+  )
+  useEffect(() => {
+    const mq = window.matchMedia('(prefers-color-scheme: dark)')
+    const onChange = (e: MediaQueryListEvent) => setSystemDark(e.matches)
+    mq.addEventListener('change', onChange)
+    return () => mq.removeEventListener('change', onChange)
+  }, [])
+  const dark = mode === 'dark' || (mode === 'system' && systemDark)
+  const configProps = useShadcnTheme(dark)
+  return (
+    <ConfigProvider locale={zhCN} {...configProps}>
+      <AntdApp>{children}</AntdApp>
+    </ConfigProvider>
+  )
+}
+
 // 登录守卫：401 统一跳转 /admin/login（§8.2）
 function RequireAuth({ children }: { children: ReactNode }) {
   const { authenticated, loading } = useAuth()
@@ -30,24 +55,26 @@ function RequireAuth({ children }: { children: ReactNode }) {
 
 export default function App() {
   return (
-    <Suspense fallback={<div className="pn-loading">加载中…</div>}>
-      <Routes>
-        <Route element={<BlogLayout />}>
-          <Route path="/" element={<Home />} />
-          <Route path="/notes/:slug" element={<Note />} />
-          <Route path="/tags" element={<TagPage />} />
-          <Route path="/tags/:tag" element={<TagPage />} />
-        </Route>
-        <Route path="/admin/login" element={<Login />} />
-        <Route element={<RequireAuth><AdminLayout /></RequireAuth>}>
-          <Route path="/admin" element={<AdminList />} />
-          <Route path="/admin/trash" element={<AdminTrash />} />
-          <Route path="/admin/settings" element={<AdminSettings />} />
-          <Route path="/admin/notes/new" element={<AdminEdit />} />
-          <Route path="/admin/notes/:id/edit" element={<AdminEdit />} />
-        </Route>
-        <Route path="*" element={<NotFound />} />
-      </Routes>
-    </Suspense>
+    <AntdProvider>
+      <Suspense fallback={<div className="pn-loading">加载中…</div>}>
+        <Routes>
+          <Route element={<BlogLayout />}>
+            <Route path="/" element={<Home />} />
+            <Route path="/notes/:slug" element={<Note />} />
+            <Route path="/tags" element={<TagPage />} />
+            <Route path="/tags/:tag" element={<TagPage />} />
+          </Route>
+          <Route path="/admin/login" element={<Login />} />
+          <Route element={<RequireAuth><AdminLayout /></RequireAuth>}>
+            <Route path="/admin" element={<AdminList />} />
+            <Route path="/admin/trash" element={<AdminTrash />} />
+            <Route path="/admin/settings" element={<AdminSettings />} />
+            <Route path="/admin/notes/new" element={<AdminEdit />} />
+            <Route path="/admin/notes/:id/edit" element={<AdminEdit />} />
+          </Route>
+          <Route path="*" element={<NotFound />} />
+        </Routes>
+      </Suspense>
+    </AntdProvider>
   )
 }