feat: assemble responsive app shell navigation

src/presentation/pages/not-found-page.jsx

@@ -0,0 +1,20 @@
+import { Link } from "react-router-dom";
+
+import { routePath } from "../../contracts/routes.js";
+import { PageHeader } from "../components/page-header.jsx";
+
+export default function NotFoundPage() {
+  return (
+    <section className="ui-page">
+      <PageHeader
+        title="페이지를 찾을 수 없습니다."
+        description="주소를 확인하거나 준비된 시작 화면으로 돌아가세요."
+      />
+      <div>
+        <Link className="ui-button" to={routePath("APP_HOME")}>
+          홈으로 이동
+        </Link>
+      </div>
+    </section>
+  );
+}