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/thumbnails.less

@@ -0,0 +1,36 @@
+//
+// Thumbnails
+// --------------------------------------------------
+
+
+// Mixin and adjust the regular image class
+.thumbnail {
+  display: block;
+  padding: @thumbnail-padding;
+  margin-bottom: @line-height-computed;
+  line-height: @line-height-base;
+  background-color: @thumbnail-bg;
+  border: 1px solid @thumbnail-border;
+  border-radius: @thumbnail-border-radius;
+  .transition(border .2s ease-in-out);
+
+  > img,
+  a > img {
+    &:extend(.img-responsive);
+    margin-left: auto;
+    margin-right: auto;
+  }
+
+  // Add a hover state for linked versions only
+  a&:hover,
+  a&:focus,
+  a&.active {
+    border-color: @link-color;
+  }
+
+  // Image captions
+  .caption {
+    padding: @thumbnail-caption-padding;
+    color: @thumbnail-caption-color;
+  }
+}