style(frontend): redesign with Miuix HyperOS design language

- Color system: Miuix dark tokens (primary #277AF7, bg #242424, surface #000)
- Components: rounded-full buttons, squircle cards (18px), glass header
- Messages: blue user bubbles, dark AI bubbles with typing animation
- Admin dashboard: stat cards with real-time service status
- Login: centered logo with gradient shadow, HyperOS input fields
- Smooth transitions and scale-on-press interactions

frontend/web/src/components/layout/AppLayout.tsx

@@ -1,18 +1,47 @@
 import { ReactNode } from 'react'
+import { Link, useLocation } from 'react-router-dom'
 import { useAuthStore } from '../../store/authStore'
-import Header from './Header'
-import Sidebar from './Sidebar'
 
 export default function AppLayout({ children }: { children: ReactNode }) {
   const { username, logout } = useAuthStore()
+  const location = useLocation()
 
   return (
-    <div className="h-screen flex flex-col bg-gray-950 text-gray-100">
-      <Header username={username} onLogout={logout} />
-      <div className="flex-1 flex overflow-hidden">
-        <Sidebar />
-        <main className="flex-1 overflow-auto">{children}</main>
-      </div>
+    <div className="h-screen flex flex-col bg-[#242424] text-[#F2F2F2]">
+      {/* Header */}
+      <header className="h-14 shrink-0 flex items-center justify-between px-4 border-b border-[#393939] bg-[#000]">
+        <Link to="/chat" className="flex items-center gap-2">
+          <div className="w-7 h-7 rounded-lg bg-[#277AF7] flex items-center justify-center">
+            <span className="text-sm font-bold text-white">C</span>
+          </div>
+          <span className="font-semibold text-base">Cyrene</span>
+        </Link>
+
+        <nav className="flex items-center gap-1">
+          <Link to="/chat"
+            className={`px-3 py-1.5 rounded-full text-sm transition-colors ${
+              location.pathname.startsWith('/chat')
+                ? 'bg-[#277AF7]/15 text-[#4788FF]'
+                : 'text-white/50 hover:text-white/80'
+            }`}
+          >聊天</Link>
+          <Link to="/admin/dashboard"
+            className={`px-3 py-1.5 rounded-full text-sm transition-colors ${
+              location.pathname.startsWith('/admin')
+                ? 'bg-[#277AF7]/15 text-[#4788FF]'
+                : 'text-white/50 hover:text-white/80'
+            }`}
+          >管理</Link>
+          <div className="w-px h-4 bg-[#393939] mx-1" />
+          <span className="text-xs text-white/40">{username}</span>
+          <button onClick={logout}
+            className="px-3 py-1.5 rounded-full text-sm text-white/40 hover:text-[#F12522] transition-colors"
+          >退出</button>
+        </nav>
+      </header>
+
+      {/* Content */}
+      <main className="flex-1 overflow-hidden">{children}</main>
     </div>
   )
 }