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/assets/libs/eonasdan-bootstrap-datetimepicker/docs/theme/browserconfig.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<browserconfig>
+  <msapplication>
+    <tile>
+      <square70x70logo src="/mstile-70x70.png"/>
+      <square150x150logo src="/mstile-150x150.png"/>
+      <square310x310logo src="/mstile-310x310.png"/>
+      <wide310x150logo src="/mstile-310x150.png"/>
+      <TileColor>#da532c</TileColor>
+    </tile>
+  </msapplication>
+</browserconfig>