feat : design system demo 페이지 구현, 리팩토링

Author: Jaeho-Site

frontend/index.html

@@ -8,12 +8,7 @@
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
     <link
       rel="stylesheet"
-      href="https://fonts.googleapis.com/css2?family=Fira+Sans+Extra+Condensed:wght@400;500;600;700;800;900&family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500;600&family=Inter:wght@400;500;600;700&family=JetBrains+Mono:wght@400;500;600&display=swap"
-    />
-    <!-- Pretendard — OLD 스펙(docs/design-system.md) 비교용 -->
-    <link
-      rel="stylesheet"
-      href="https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/variable/pretendardvariable.min.css"
+      href="https://fonts.googleapis.com/css2?family=Fira+Sans+Extra+Condensed:wght@400;500;600;700;800;900&family=Geist:wght@400;500;600;700&family=Geist+Mono:wght@400;500;600&family=Inter:wght@400;500;600;700&display=swap"
     />
     <title>StackUp</title>
   </head>