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/less/bootstrap-less/mixins/table-row.less

@@ -0,0 +1,28 @@
+// Tables
+
+.table-row-variant(@state; @background) {
+  // Exact selectors below required to override `.table-striped` and prevent
+  // inheritance to nested tables.
+  .table > thead > tr,
+  .table > tbody > tr,
+  .table > tfoot > tr {
+    > td.@{state},
+    > th.@{state},
+    &.@{state} > td,
+    &.@{state} > th {
+      background-color: @background;
+    }
+  }
+
+  // Hover states for `.table-hover`
+  // Note: this is not available for cells or rows within `thead` or `tfoot`.
+  .table-hover > tbody > tr {
+    > td.@{state}:hover,
+    > th.@{state}:hover,
+    &.@{state}:hover > td,
+    &:hover > .@{state},
+    &.@{state}:hover > th {
+      background-color: darken(@background, 5%);
+    }
+  }
+}