feat: 后端全量更新 - 含所有本次需求

- Contract.php: 返回合约账户余额(balance_contract)
- My.php: 地址管理增加BTC/ETH
- AppContract.php: 一键平仓(closeall)
- AppProxy.php: 代理专属注册链接 + 分级权限(L1/L2)
- site.php: 手续费减半(0.018→0.009)
- agent_permission_setup.sql: 代理权限SQL
- crypto_news_crawler.py: 新闻自动采集脚本

application/index/controller/Ajax.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace app\index\controller;
+
+use app\common\controller\Frontend;
+use think\Lang;
+
+/**
+ * Ajax异步请求接口
+ * @internal
+ */
+class Ajax extends Frontend
+{
+
+    protected $noNeedLogin = ['lang', 'upload'];
+    protected $noNeedRight = ['*'];
+    protected $layout = '';
+
+    /**
+     * 加载语言包
+     */
+    public function lang()
+    {
+        header('Content-Type: application/javascript');
+        header("Cache-Control: public");
+        header("Pragma: cache");
+
+        $offset = 30 * 60 * 60 * 24; // 缓存一个月
+        header("Expires: " . gmdate("D, d M Y H:i:s", time() + $offset) . " GMT");
+
+        $controllername = input("controllername");
+        $this->loadlang($controllername);
+        //强制输出JSON Object
+        $result = jsonp(Lang::get(), 200, [], ['json_encode_param' => JSON_FORCE_OBJECT | JSON_UNESCAPED_UNICODE]);
+        return $result;
+    }
+
+    /**
+     * 上传文件
+     */
+    public function upload()
+    {
+        return action('api/common/upload');
+    }
+
+}