完善产品购买页面，抽取公共组件，优化导航链接

src/app/admin/extract/page.tsx

@@ -0,0 +1,10 @@
+import {ReactNode} from 'react'
+
+export type ExtractPageProps = {
+}
+
+export default async function ExtractPage(props: ExtractPageProps) {
+  return (
+    <main></main>
+  )
+}