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/less/utilities.less

@@ -0,0 +1,57 @@
+// stylelint-disable declaration-no-important
+
+//
+// Utility classes
+// --------------------------------------------------
+
+
+// Floats
+// -------------------------
+
+.clearfix {
+  .clearfix();
+}
+.center-block {
+  .center-block();
+}
+.pull-right {
+  float: right !important;
+}
+.pull-left {
+  float: left !important;
+}
+
+
+// Toggling content
+// -------------------------
+
+// Note: Deprecated .hide in favor of .hidden or .sr-only (as appropriate) in v3.0.1
+.hide {
+  display: none !important;
+}
+.show {
+  display: block !important;
+}
+.invisible {
+  visibility: hidden;
+}
+.text-hide {
+  .text-hide();
+}
+
+
+// Hide from screenreaders and browsers
+//
+// Credit: HTML5 Boilerplate
+
+.hidden {
+  display: none !important;
+}
+
+
+// For Affix plugin
+// -------------------------
+
+.affix {
+  position: fixed;
+}