refactor: restructure next.config.js for clarity and organization

next.config.js

@@ -1,4 +1,7 @@
+// next.config.js
 /** @type {import('next').NextConfig} */
-module.exports = {
+const nextConfig = {
+  distDir: 'build',     // 改变默认的 .next 目录
   reactStrictMode: true,
-};
+};
+module.exports = nextConfig;