refactor: 完成静态网站转换，移除所有 CMS 和动态功能

- 删除数据库相关代码 (src/db/)
- 删除 API 路由 (src/app/api/)
- 删除认证相关代码 (src/lib/auth/, src/providers/)
- 删除监控和安全中间件 (src/lib/security/, src/lib/monitoring/)
- 删除 hooks (use-news, use-products, use-services)
- 更新组件为静态数据源
- 添加 nginx 静态配置和部署脚本
- 添加 static-link 组件

src/app/(marketing)/cases/[id]/client.tsx

@@ -1,7 +1,7 @@
 'use client';
 
 import { useEffect, useRef, useState } from 'react';
-import Link from 'next/link';
+import { StaticLink } from '@/components/ui/static-link';
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
 import { BackButton } from '@/components/ui/back-button';
@@ -99,7 +99,7 @@ export function CaseDetailClient({ caseItem }: CaseDetailClientProps) {
                     我们如何智连未来
                   </h2>
                 </div>
-                <div className="prose prose-sm max-w-none">
+                <div className="prose prose-base max-w-none [&_h3]:text-xl [&_h3]:font-semibold [&_h3]:text-[#1C1C1C] [&_h3]:mt-8 [&_h3]:mb-4 [&_p]:text-[#5C5C5C] [&_p]:leading-[1.8] [&_p]:mb-4 [&_p]:text-base">
                   <div dangerouslySetInnerHTML={{ __html: caseItem.content }} />
                 </div>
               </section>
@@ -237,9 +237,9 @@ export function CaseDetailClient({ caseItem }: CaseDetailClientProps) {
                   className="w-full bg-white text-[#C41E3A] hover:bg-white/90"
                   asChild
                 >
-                  <Link href="/contact">
+                  <StaticLink href="/contact">
                     联系我们
-                  </Link>
+                  </StaticLink>
                 </Button>
               </div>
             </div>