fix: PC 端全站移动端响应式修复

Critical:
- header.tsx: 手机菜单按钮 flex-row→flex-col, 修复 w-full 溢出
- compare/page.tsx: 参数面板 grid-cols-3→grid-cols-1 sm:grid-cols-3

High:
- sandbox/page.tsx: header 区 flex-wrap + 模型选择器 w-48→w-40 sm:w-48
- member/page.tsx: 功能对比行 grid 布局替代 flex, 防溢出
- workshop/page.tsx: 编辑区 flex-col sm:flex-row + 按钮组 flex-wrap

Medium:
- analytics/page.tsx: domain name truncate
- skills/[id]: CTA 按钮 w-full sm:w-auto

frontend/src/app/skills/[id]/client.tsx

@@ -68,7 +68,7 @@ export default function SkillDetailPage() {
         </div>
 
         <Link href={`/sandbox?skill=${skill.id}`}
-          className="inline-flex px-5 py-2.5 bg-brand-600 text-white rounded-xl text-sm font-medium hover:bg-brand-700 transition-colors">
+          className="w-full sm:w-auto inline-flex px-5 py-2.5 bg-brand-600 text-white rounded-xl text-sm font-medium hover:bg-brand-700 transition-colors justify-center">
           {t.skills.apply}
         </Link>
       </div>