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/font-awesome/less/list.less

@@ -0,0 +1,19 @@
+// List Icons
+// -------------------------
+
+.@{fa-css-prefix}-ul {
+  padding-left: 0;
+  margin-left: @fa-li-width;
+  list-style-type: none;
+  > li { position: relative; }
+}
+.@{fa-css-prefix}-li {
+  position: absolute;
+  left: -@fa-li-width;
+  width: @fa-li-width;
+  top: (2em / 14);
+  text-align: center;
+  &.@{fa-css-prefix}-lg {
+    left: (-@fa-li-width + (4em / 14));
+  }
+}