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/layout/footer.tsx

@@ -5,7 +5,7 @@ import { COMPANY_INFO, NAVIGATION_V2, MEGA_DROPDOWN_DATA } from '@/lib/constants
 
 export function Footer() {
   return (
-    <footer className="bg-[var(--color-footer-bg)] text-white py-16" data-testid="footer" role="contentinfo">
+    <footer className="bg-[var(--color-footer-bg)] text-white py-12 md:py-16" data-testid="footer" role="contentinfo">
       <div className="container-wide">
         <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-5 gap-10 lg:gap-8">
           <div data-testid="card-brand" className="lg:col-span-2">
@@ -107,7 +107,7 @@ export function Footer() {
           </div>
         </div>
 
-        <div className="border-t border-[var(--color-footer-border)] mt-12 pt-8 pb-24 md:pb-8">
+        <div className="border-t border-[var(--color-footer-border)] mt-12 pt-8 pb-24 md:pb-8" style={{ paddingBottom: 'calc(5rem + env(safe-area-inset-bottom, 0px))' }}>
           <div className="flex flex-col md:flex-row justify-between items-center gap-4">
             <p className="text-[var(--color-footer-text-muted)] text-sm">
               © {new Date().getFullYear()} {COMPANY_INFO.name}. All rights reserved.