feat: global shell — header, footer, sidebars, and layout integration

app/(main)/layout.tsx

@@ -1,20 +1,12 @@
+import { Footer } from "@/components/footer"
+import { Header } from "@/components/header"
+
 export default function MainLayout({ children }: { children: React.ReactNode }) {
   return (
     <div className="flex min-h-screen flex-col">
-      <header className="border-b">
-        <nav className="container mx-auto flex h-16 items-center justify-between px-4">
-          <span className="text-xl font-bold">聚玩</span>
-          <div className="flex items-center gap-4">
-            <span className="text-sm text-muted-foreground">导航占位</span>
-          </div>
-        </nav>
-      </header>
+      <Header />
       <main className="flex-1">{children}</main>
-      <footer className="border-t py-6">
-        <div className="container mx-auto px-4 text-center text-sm text-muted-foreground">
-          © 聚玩 - 游戏陪玩服务平台
-        </div>
-      </footer>
+      <Footer />
     </div>
   )
 }