feat: add shadcn theme switcher

frontend/src/app/App.tsx

@@ -1,14 +1,17 @@
 import { AppShell } from './layout/AppShell'
 import { Router } from './router'
+import { AppThemeProvider } from '@/components/app/AppThemeProvider'
 import { AuthProvider, useAuth } from '@/features/auth/AuthProvider'
 import { LoginPage } from '@/features/auth/LoginPage'
 import { Skeleton } from '@/components/ui/skeleton'
 
 export function App() {
   return (
-    <AuthProvider>
+    <AppThemeProvider>
-      <AppContent />
+      <AuthProvider>
-    </AuthProvider>
+        <AppContent />
+      </AuthProvider>
+    </AppThemeProvider>
   )
 }
 

frontend/src/components/app/AppThemeProvider.tsx

@@ -0,0 +1,14 @@
+import type * as React from 'react'
+import { ThemeProvider } from 'next-themes'
+
+type AppThemeProviderProps = {
+  children: React.ReactNode
+}
+
+export function AppThemeProvider({ children }: AppThemeProviderProps) {
+  return (
+    <ThemeProvider attribute="class" defaultTheme="system" enableSystem disableTransitionOnChange>
+      {children}
+    </ThemeProvider>
+  )
+}

frontend/src/components/app/AppThemeToggle.tsx

@@ -0,0 +1,53 @@
+import { Laptop, Moon, Sun } from 'lucide-react'
+import { useTheme } from 'next-themes'
+
+import { Button } from '@/components/ui/button'
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuGroup,
+  DropdownMenuLabel,
+  DropdownMenuRadioGroup,
+  DropdownMenuRadioItem,
+  DropdownMenuSeparator,
+  DropdownMenuTrigger
+} from '@/components/ui/dropdown-menu'
+
+const themeOptions = [
+  { value: 'light', label: '亮色', icon: Sun },
+  { value: 'dark', label: '暗色', icon: Moon },
+  { value: 'system', label: '跟随系统', icon: Laptop }
+]
+
+export function AppThemeToggle() {
+  const { theme = 'system', setTheme } = useTheme()
+  const activeTheme = themeOptions.find((option) => option.value === theme) ?? themeOptions[2]
+  const ActiveIcon = activeTheme.icon
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="ghost" size="icon" aria-label={`主题：${activeTheme.label}`}>
+          <ActiveIcon data-icon="inline-start" />
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end" className="w-40">
+        <DropdownMenuLabel>界面主题</DropdownMenuLabel>
+        <DropdownMenuSeparator />
+        <DropdownMenuGroup>
+          <DropdownMenuRadioGroup value={theme} onValueChange={setTheme}>
+            {themeOptions.map((option) => {
+              const Icon = option.icon
+              return (
+                <DropdownMenuRadioItem key={option.value} value={option.value}>
+                  <Icon data-icon="inline-start" />
+                  {option.label}
+                </DropdownMenuRadioItem>
+              )
+            })}
+          </DropdownMenuRadioGroup>
+        </DropdownMenuGroup>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  )
+}

frontend/src/components/app/AppTopbar.tsx

@@ -1,5 +1,6 @@
 import { Bell, ChevronRight, LogOut, Menu, UserRound } from 'lucide-react'
 
+import { AppThemeToggle } from '@/components/app/AppThemeToggle'
 import { Badge } from '@/components/ui/badge'
 import { Button } from '@/components/ui/button'
 import { Separator } from '@/components/ui/separator'
@@ -34,6 +35,7 @@ export function AppTopbar({ onMobileMenuClick }: AppTopbarProps) {
         <Button variant="ghost" size="icon" aria-label="通知">
           <Bell data-icon="inline-start" />
         </Button>
+        <AppThemeToggle />
         <Button variant="ghost" className="hidden gap-2 sm:inline-flex">
           <UserRound data-icon="inline-start" />
           <span>{user?.display_name || user?.username || '当前用户'}</span>

frontend/src/styles/globals.css

@@ -39,6 +39,41 @@
     --sidebar-ring: 213 52% 32%;
   }
 
+  .dark {
+    --background: 222 28% 8%;
+    --foreground: 214 24% 94%;
+    --surface: 222 26% 11%;
+    --muted: 219 22% 17%;
+    --muted-foreground: 215 14% 70%;
+    --border: 219 20% 24%;
+    --primary: 186 52% 46%;
+    --primary-foreground: 222 28% 8%;
+    --success: 151 55% 46%;
+    --warning: 38 86% 58%;
+    --danger: 0 70% 60%;
+    --info: 204 76% 58%;
+    --ai-accent: 186 52% 46%;
+    --card: 222 26% 11%;
+    --card-foreground: 214 24% 94%;
+    --popover: 222 26% 11%;
+    --popover-foreground: 214 24% 94%;
+    --secondary: 219 22% 17%;
+    --secondary-foreground: 214 24% 94%;
+    --accent: 219 22% 17%;
+    --accent-foreground: 214 24% 94%;
+    --destructive: 0 70% 60%;
+    --input: 219 20% 24%;
+    --ring: 186 52% 46%;
+    --sidebar: 222 32% 11%;
+    --sidebar-foreground: 214 24% 92%;
+    --sidebar-primary: 186 52% 46%;
+    --sidebar-primary-foreground: 222 28% 8%;
+    --sidebar-accent: 219 26% 20%;
+    --sidebar-accent-foreground: 0 0% 100%;
+    --sidebar-border: 219 24% 24%;
+    --sidebar-ring: 186 52% 46%;
+  }
+
   body {
     margin: 0;
     background: hsl(var(--background));