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/fastadmin/.csslintrc

@@ -0,0 +1,23 @@
+{
+  "adjoining-classes": false,
+  "box-sizing": false,
+  "box-model": false,
+  "compatible-vendor-prefixes": false,
+  "floats": false,
+  "font-sizes": false,
+  "gradients": false,
+  "important": false,
+  "known-properties": false,
+  "outline-none": false,
+  "qualified-headings": false,
+  "regex-selectors": false,
+  "shorthand": false,
+  "text-indent": false,
+  "unique-headings": false,
+  "universal-selector": false,
+  "unqualified-attributes": false,
+  "ids": false,
+  "fallback-colors": false,
+  "vendor-prefix": false,
+  "import": false
+}