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

.env.sample

@@ -0,0 +1,11 @@
+[app]
+debug = false
+trace = false
+
+[database]
+hostname = 127.0.0.1
+database = fastadmin
+username = root
+password = root
+hostport = 3306
+prefix = fa_