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-select/js/i18n/defaults-nl_NL.js

@@ -0,0 +1,15 @@
+/*
+ * Translated default messages for bootstrap-select.
+ * Locale: NL (Dutch; Nederlands)
+ * Region: NL (Europe)
+ * Author: Daan Rosbergen (Badmuts)
+ */
+(function ($) {
+  $.fn.selectpicker.defaults = {
+    noneSelectedText: 'Niets geselecteerd',
+    noneResultsText: 'Geen resultaten gevonden voor {0}',
+    countSelectedText: '{0} van {1} geselecteerd',
+    maxOptionsText: ['Limiet bereikt ({n} {var} max)', 'Groep limiet bereikt ({n} {var} max)', ['items', 'item']],
+    multipleSeparator: ', '
+  };
+})(jQuery);