fix(autoload): one PSR-4 type per payment/widget file

PSR-4 split left GatewayInterface/Gateway duplicated across files;
loading BalanceGateway redeclared the interface. Strip sibling types
from polluted files (payment + widgets) so each path owns one type.

src/AKSRT/Payment/GatewayInterface.php

@@ -7,17 +7,6 @@ namespace AKSRT\Payment;
 
 defined('ABSPATH') || exit;
 
-/**
- * AKSRT Payment Gateway — 支付网关适配器层
- *
- * 定义支付网关统一接口和基础实现。
- * 具体网关（支付宝、微信支付等）通过子类实现。
- *
- * @package AKSRT
- */
-
-defined('ABSPATH') || exit;
-
 /**
  * 支付网关统一接口
  */