refactor(apk): 优化安装包接口响应结构

- 将响应数据改为只返回 url 字段
- 移除附件对象的完整数组返回
- 统一响应格式为标准 URL 结构

application/api/controller/Apk.php

@@ -101,7 +101,10 @@ class Apk extends Api
         if (!$attachment) {
             $this->error('暂无安装包');
         }
+        $response = [
+            'url' => $this->request->domain() . $attachment->url,
+        ];
 
-        $this->success('获取成功', $attachment->toArray());
+        $this->success('获取成功', $response);
     }
 }