refactor: 将取消订单接口从 icbcRefundAPI 替换为 billCancelUnpaidAPI

- 使用 billCancelUnpaidAPI 替代 icbcRefundAPI
- 传参和调用方式保持不变
- 更适合取消未支付订单的场景

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

@@ -7,7 +7,7 @@
  */
 import Taro from '@tarojs/taro'
 import { wxPayAPI } from '@/api/wx/pay'
-import { icbcRefundAPI } from '@/api/index'
+import { billCancelUnpaidAPI } from '@/api/index'
 import { ENABLE_REPAY_FEATURE } from '@/utils/config'
 
 /**
@@ -70,7 +70,7 @@ export const wechat_pay = async ({ pay_id }) => {
     // 自动取消订单
     Taro.showLoading({ title: '取消订单中...' })
     try {
-      const { code } = await icbcRefundAPI({ pay_id: normalized_pay_id })
+      const { code } = await billCancelUnpaidAPI({ pay_id: normalized_pay_id })
       Taro.hideLoading()
       if (code) {
         // 取消成功，更新提示文案