feat: initial project setup for Meme Studio

Next.js 14 App Router application for managing homophone pun game levels:

- Better Auth with Prisma adapter for authentication
- MySQL database with Prisma ORM
- Level CRUD operations with drag-and-drop reordering
- Tencent COS integration for image uploads
- shadcn/ui components with Tailwind CSS
- TanStack Query for server state management

components/layout/header.tsx

@@ -0,0 +1,27 @@
+'use client'
+
+import { useSession } from '@/lib/auth-client'
+import { Spinner } from '@/components/ui/spinner'
+
+export function Header() {
+  const { data: session, isPending } = useSession()
+
+  if (isPending) {
+    return (
+      <header className="h-16 border-b bg-white flex items-center justify-center px-6">
+        <Spinner size="sm" />
+      </header>
+    )
+  }
+
+  return (
+    <header className="h-16 border-b bg-white flex items-center justify-between px-6">
+      <h2 className="text-lg font-semibold">关卡配置管理</h2>
+      <div className="flex items-center gap-4">
+        <span className="text-sm text-gray-500">
+          {session?.user?.email}
+        </span>
+      </div>
+    </header>
+  )
+}