Implement homepage auto-redirect based on browser language

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>

Author: Copilot

packages/site/app/page.tsx

@@ -1,10 +1,36 @@
 import { createI18nMiddleware } from 'fumadocs-core/i18n/middleware';
 import { i18n } from '@/lib/i18n';
+import { NextResponse, NextRequest, NextFetchEvent } from 'next/server';
 
-export default createI18nMiddleware(i18n);
+// Create fumadocs middleware
+const fumadocsMiddleware = createI18nMiddleware(i18n);
+
+export default function proxy(request: NextRequest, event: NextFetchEvent) {
+  const path = request.nextUrl.pathname;
+  
+  // Handle root path separately with custom language detection
+  if (path === '/') {
+    const acceptLanguage = request.headers.get('accept-language') || '';
+    
+    // Simple language detection: check if zh is in Accept-Language
+    if (acceptLanguage.toLowerCase().includes('zh')) {
+      // Redirect to Chinese docs
+      const url = request.nextUrl.clone();
+      url.pathname = '/cn/docs';
+      return NextResponse.redirect(url);
+    } else {
+      // Redirect to default language (English)
+      const url = request.nextUrl.clone();
+      url.pathname = '/en/docs';
+      return NextResponse.redirect(url);
+    }
+  }
+  
+  // For all other paths, pass through to fumadocs middleware
+  return fumadocsMiddleware(request, event);
+}
 
 export const config = {
   // Matcher ignoring `/_next/` and `/api/`
-  // You may need to adjust it to ignore static assets in `/public` folder
   matcher: ['/((?!api|_next/static|_next/image|favicon.ico|logo.svg).*)'],
 };