feat: 优化全局样式与组件视觉升级

- 更新 globals.css 全局样式
- 优化 not-found 404 页面
- 升级 footer, mega-dropdown, mobile-tab-bar 布局组件
- 改进 challenge, cta, hero 等核心 section 组件
- 优化 challenge-card, ink-glow-card, product-card 等 UI 组件
- 更新产品常量配置

src/components/sections/social-proof-section.tsx

@@ -31,7 +31,7 @@ export function SocialProofSection() {
   const shouldReduceMotion = useReducedMotion();
 
   return (
-    <section id="social-proof" role="region" aria-labelledby="social-proof-heading" className="py-16 md:py-20 bg-[var(--color-bg-section)]">
+    <section id="social-proof" role="region" aria-labelledby="social-proof-heading" className="py-12 md:py-16 lg:py-20 bg-[var(--color-bg-section)]">
       <div className="container-wide">
         <motion.div
           initial={shouldReduceMotion ? {} : { opacity: 0, y: 20 }}