[Feat] WTH-151: 어드민 레이아웃 구현

src/app/(private)/admin/layout.tsx

@@ -1,7 +1,20 @@
+import { Header } from '@/components/admin/layout/Header';
+import { LNB } from '@/components/admin/layout/LNB';
+
 export default function AdminLayout({
   children,
 }: Readonly<{
   children: React.ReactNode;
 }>) {
-  return <div data-admin>{children}</div>;
+  return (
+    <div data-admin className="flex h-screen flex-col">
+      <div className="flex flex-1 overflow-hidden">
+        <LNB />
+        <main className="bg-container-neutral-alternative flex-1 overflow-auto">
+          <Header />
+          {children}
+        </main>
+      </div>
+    </div>
+  );
 }