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/bootstrap-table/dist/extensions/sticky-header/bootstrap-table-sticky-header.css

@@ -0,0 +1,22 @@
+/**
+ * @author vincent loh <vincent.ml@gmail.com>
+ * @version: v1.0.0
+ * https://github.com/vinzloh/bootstrap-table/
+ * Sticky header for bootstrap-table
+ */
+
+.fix-sticky {
+    position: fixed;
+    z-index: 100;
+}
+.fix-sticky thead {
+    background: #fff;
+}
+
+.fix-sticky thead th,
+.fix-sticky thead th:first-child {
+    border-left: 0;
+    border-right: 0;
+    border-bottom: 1px solid #eee;
+    border-radius: 0;
+}