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

addons/kefu/library/GatewayWorker/composer.json

@@ -0,0 +1,9 @@
+{
+    "name"  : "workerman/gateway-worker-demo",
+    "keywords": ["distributed","communication"],
+    "homepage": "http://www.workerman.net",
+    "license" : "MIT",
+    "require": {
+        "workerman/gateway-worker" : ">=3.0.0"
+    }
+}