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

public/GoJS-master/api/assets/licensing.txt

@@ -0,0 +1,8 @@
+Files in this directory without licensing info use the following:
+/**
+ * Copyright (c) 2015-2017 Sebastian Lenz.
+ * Licensed under the Apache License 2.0.
+ */
+ 
+icons.png has been modified for variation in colors.
+