feat: add stage 0 foundation

frontend/src/features/design-system/DesignSystemPreview.tsx

@@ -0,0 +1,48 @@
+import { AppPageHeader } from '@/components/app/AppPageHeader'
+import { AppPriorityBadge } from '@/components/app/AppPriorityBadge'
+import { AppStatusBadge } from '@/components/app/AppStatusBadge'
+import { Badge } from '@/components/ui/badge'
+import { Button } from '@/components/ui/button'
+import { Card, CardContent, CardHeader } from '@/components/ui/card'
+
+export function DesignSystemPreview() {
+  return (
+    <main className="min-h-screen bg-background p-6 text-foreground">
+      <div className="mx-auto flex max-w-6xl flex-col gap-6">
+        <AppPageHeader
+          title="设计系统预览"
+          description="业务页面必须基于这些 token 和组件开发。"
+          actions={<Button>创建工单</Button>}
+        />
+
+        <Card>
+          <CardHeader>
+            <h2 className="text-sm font-medium">Buttons</h2>
+          </CardHeader>
+          <CardContent className="flex flex-wrap gap-2">
+            <Button>Primary</Button>
+            <Button variant="secondary">Secondary</Button>
+            <Button variant="ghost">Ghost</Button>
+            <Button variant="danger">Danger</Button>
+          </CardContent>
+        </Card>
+
+        <Card>
+          <CardHeader>
+            <h2 className="text-sm font-medium">Badges</h2>
+          </CardHeader>
+          <CardContent className="flex flex-wrap gap-2">
+            <Badge>Default</Badge>
+            <Badge variant="success">Success</Badge>
+            <Badge variant="warning">Warning</Badge>
+            <Badge variant="danger">Danger</Badge>
+            <Badge variant="info">Info</Badge>
+            <Badge variant="ai">AI</Badge>
+            <AppStatusBadge status="in_progress" />
+            <AppPriorityBadge priority="urgent" />
+          </CardContent>
+        </Card>
+      </div>
+    </main>
+  )
+}