feat: PublicShell + TopNav + 홈 v6 (ai_music_creator 참조)

- 사이드바 대시보드는 /admin, /mypage 에서만 사용
- 공개 페이지는 상단 TopNav + 다크 footer(PublicShell)
- 홈 v6: Hero + Evidence + Before/After + Toolkit + 3-Step + Other Products

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/components/DashboardShell.tsx

@@ -3,19 +3,26 @@
 import { useState } from 'react';
 import { usePathname } from 'next/navigation';
 import Sidebar from './Sidebar';
+import PublicShell from './PublicShell';
 
 const STANDALONE_PATHS = ['/login', '/signup', '/admin'];
+const SIDEBAR_PATHS = ['/mypage'];
 
 export default function DashboardShell({ children }: { children: React.ReactNode }) {
   const [sidebarOpen, setSidebarOpen] = useState(false);
   const pathname = usePathname();
 
   const isStandalone = STANDALONE_PATHS.some((p) => pathname.startsWith(p));
+  const useSidebar = SIDEBAR_PATHS.some((p) => pathname.startsWith(p));
 
   if (isStandalone) {
     return <>{children}</>;
   }
 
+  if (!useSidebar) {
+    return <PublicShell>{children}</PublicShell>;
+  }
+
   return (
     <div className="dashboard-layout">
       <Sidebar isOpen={sidebarOpen} onClose={() => setSidebarOpen(false)} />