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/Sortable/CONTRIBUTING.md

@@ -0,0 +1,26 @@
+# Contribution Guidelines
+
+### Issue
+
+ 1. Try [master](https://github.com/SortableJS/Sortable/tree/master/)-branch, perhaps the problem has been solved;
+ 2. [Use the search](https://github.com/SortableJS/Sortable/search?type=Issues&q=problem), maybe already have an answer;
+ 3. If not found, create example on [jsbin.com (draft)](https://jsbin.com/kamiwez/edit?html,js,output) and describe the problem.
+
+---
+
+### Pull Request
+
+ 1. Only request to merge with the [master](https://github.com/SortableJS/Sortable/tree/master/)-branch.
+ 2. Only modify source files, **do not commit the resulting build**
+
+### Setup
+
+ 1. Fork the repo on [github](https://github.com)
+ 2. Clone locally
+ 3. Run `npm i` in the local repo
+
+### Building
+
+ - For development, build the `./Sortable.js` file using the command `npm run build:umd:watch`
+ - To build everything and minify it, run `npm run build`
+ - Do not commit the resulting builds in any pull request – they will be generated at release