feat(api): 添加取消未支付预约单接口

新增 BILL_CANCEL_UNPAID API 端点及对应的 billCancelUnpaidAPI 函数，用于支持前端取消未支付预约单的功能。

 /*
  * @Date: 2023-08-24 09:42:27
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2026-01-22 09:41:23
+ * @LastEditTime: 2026-01-30 17:04:48
  * @FilePath: /xyxBooking-weapp/src/api/index.js
  * @Description: 文件描述
  */
@@ -26,6 +26,7 @@ const Api = {
   QRCODE_STATUS: '/srv/?a=api&t=qrcode_status',
   BILL_LIST: '/srv/?a=api&t=bill_list',
   BILL_OFFLINE_ALL: '/srv/?a=api&t=bill_all_info',
+  BILL_CANCEL_UNPAID: '/srv/?a=api&t=bill_cancel_unpaid',
   ICBC_REFUND: '/srv/?a=icbc_refund',
   BILL_PREPARE: '/srv/?a=api&t=bill_person',
   // BILL_PAY_STATUS: '/srv/?a=api&t=bill_pay_status',
@@ -159,6 +160,13 @@ export const billOfflineAllAPI = params => fn(fetch.get(Api.BILL_OFFLINE_ALL, pa
 export const icbcRefundAPI = params => fn(fetch.post(Api.ICBC_REFUND, params))
 
 /**
+ * @description: 取消未支付预约单
+ * @param {String} pay_id 预约单ID
+ * @returns {String}
+ */
+export const billCancelUnpaidAPI = params => fn(fetch.post(Api.BILL_CANCEL_UNPAID, params))
+
+/**
  * @description: 预约单的参观者列表
  * @param {String}
  * @returns {String}