feat: 初始化进销存数据开放平台项目

初始化完整的前后端项目结构，包含ThinkPHP后端API服务和Next.js前端管理系统，添加基础配置、中间件、模型、路由等核心代码，以及项目文档和静态资源。

thinkphp/app/middleware/CrossDomain.php

@@ -0,0 +1,24 @@
+<?php
+namespace app\middleware;
+
+class CrossDomain
+{
+    public function handle($request, \Closure $next)
+    {
+        $header = [
+            'Access-Control-Allow-Origin'  => '*',
+            'Access-Control-Allow-Methods' => 'GET,POST,PUT,PATCH,DELETE,OPTIONS',
+            'Access-Control-Allow-Headers' => 'Content-Type,Authorization,Token,X-Requested-With,X-API-Key,X-Timestamp,X-Sign',
+            'Access-Control-Max-Age'       => 1800,
+        ];
+
+        if ($request->method() == 'OPTIONS') {
+            return response('', 204)->header($header);
+        }
+
+        $response = $next($request);
+        $response->header($header);
+
+        return $response;
+    }
+}