feat: update API reference and redirect for API documentation

- Change API reference links to point to the new documentation site
- Implement redirect for 'api-reference' paths to the new API documentation
- Enhance API overview with additional sections and callouts for better user guidance
- Remove outdated sections and files to streamline the documentation

Author: cunoe

app/(home)/page.tsx

@@ -15,7 +15,7 @@ export default function HomePage() {
         User Guide
       </Link>
       <Link
-        href="/docs/api-reference"
+        href="https://api-docs.multipost.app/"
         className="px-6 py-3 bg-fd-primary text-fd-primary-foreground rounded-md font-medium hover:bg-fd-primary/90 transition-colors"
       >
         API Reference

app/docs/[[...slug]]/page.tsx

@@ -5,14 +5,20 @@ import {
   DocsDescription,
   DocsTitle,
 } from 'fumadocs-ui/page';
-import { notFound } from 'next/navigation';
+import { notFound, redirect } from 'next/navigation';
 import { createRelativeLink } from 'fumadocs-ui/mdx';
 import { getMDXComponents } from '@/mdx-components';
 
 export default async function Page(props: {
   params: Promise<{ slug?: string[] }>;
 }) {
   const params = await props.params;
+  
+  // 检查是否是 api-reference 开头的路径
+  if (params.slug?.[0] === 'api-reference') {
+    redirect('https://api-docs.multipost.app/');
+  }
+
   const page = source.getPage(params.slug);
   if (!page) notFound();