feat: 订场页改为网格时间表，支持多场地多时段选择

- private/index.vue 重写为场地×时间网格，双向滚动，sticky表头
- 当前时间红线指示，已过时灰块/已占用浅红/已选中蓝色
- 支持多场地连续时段选择，非连续会提示
- 日期改为近7天，Tab栏样式与约课页统一
- 底部按钮：未选时全宽长条，选中后显示摘要+小按钮
- privateBooking.js 新增 getPrivateBookingGrid API
- quote/create 改为 items[] 格式，每场地独立时间段
- confirm.vue 按 items 逐条展示
- pages/private/index.vue onShow 自动刷新
- .env 冰场馆URL修正

miniprogram/src/pages/private/index.vue

@@ -7,12 +7,22 @@
 
 <script setup>
 import { ref } from 'vue'
+import { onShow } from '@dcloudio/uni-app'
 import { getStoredVenue } from '@/utils/venue'
 import ComprehensivePrivate from '@/pages/comprehensive/private/index.vue'
 import IcePrivate from '@/pages/ice/private/index.vue'
 
 const isComprehensive = getStoredVenue() === 'comprehensive'
 const contentRef = ref()
+let isFirstShow = true
+
+onShow(() => {
+  if (isFirstShow) {
+    isFirstShow = false
+    return
+  }
+  contentRef.value?.refresh?.()
+})
 </script>
 
 <style lang="scss" scoped>