feat: 补齐预约下单售后链路，并接入礼品卡结算

立即购买先选时段再结算，免物流地址，售后按数量退款；同步接入礼品卡入口。

Co-authored-by: Cursor <cursoragent@cursor.com>

api/appointment.js

@@ -0,0 +1,52 @@
+/**
+ * 预约服务买家端 API
+ */
+import { http, Method } from '@/utils/request.js'
+
+/** 查询可预约时段 */
+export function listSlots(skuId, slotDate) {
+  return http.request({
+    url: '/buyer/appointment/slots',
+    method: Method.GET,
+    needToken: true,
+    params: { skuId, slotDate },
+  })
+}
+
+/** 绑定预约结算上下文（addToCart 后、createTrade 前） */
+export function bindCheckout(data) {
+  return http.request({
+    url: '/buyer/appointment/checkout/bind',
+    method: Method.POST,
+    needToken: true,
+    data,
+  })
+}
+
+/** 预约商品扩展配置 */
+export function getGoodsExt(goodsId) {
+  return http.request({
+    url: `/buyer/appointment/goods/${goodsId}/ext`,
+    method: Method.GET,
+    needToken: false,
+  })
+}
+
+/** 买家预约订单详情（时段、核销码） */
+export function getAppointmentOrderDetail(orderSn) {
+  return http.request({
+    url: `/buyer/appointment/order/${orderSn}`,
+    method: Method.GET,
+    needToken: true,
+  })
+}
+
+/** 改期申请 */
+export function requestReschedule(orderSn, payload) {
+  return http.request({
+    url: `/buyer/appointment/orders/${orderSn}/reschedule`,
+    method: Method.POST,
+    needToken: true,
+    data: payload || {},
+  })
+}