fix(product-gift): :class 改用 _selected 状态字段，移除方法调用

cfc-frontend/pages/discover-detail/product-detail/product-detail.vue

@@ -32,7 +32,7 @@
             <view
               v-for="item in giftItems"
               :key="getGiftItemKey(item)"
-              :class="isGiftSelected(item) ? 'gift-select-item gift-select-item-active' : 'gift-select-item'"
+              :class="item._selected ? 'gift-select-item gift-select-item-active' : 'gift-select-item'"
               @click="toggleGift(item)"
             >
               <image v-if="item.giftType === 'product' && item.giftProductImage" class="gift-select-img" :src="getImageUrl(item.giftProductImage)" mode="aspectFill" />
@@ -41,7 +41,7 @@
                 <text class="gift-select-name">{{ item.giftType === 'product' ? item.giftProductName : (item.cfValue + ' CF值') }}</text>
                 <text class="gift-select-type">{{ item.giftType === 'product' ? '赠品商品' : 'CF值赠品' }}</text>
               </view>
-              <view v-if="isGiftSelected(item)" class="gift-select-check">✓</view>
+              <view v-if="item._selected" class="gift-select-check">✓</view>
             </view>
           </view>
         </view>
@@ -186,8 +186,6 @@ export default {
       isMember: false,
       memberLevel: 'FREE',
       bundleItems: []
-      // 赠品选择（giftConfigs 来自商品详情，当前用户等级匹配）
-      , selectedGiftIds: []
     }
   },
   computed: {
@@ -374,6 +372,16 @@ export default {
         if (res.code === 200 && res.data) {
           that.product = res.data
           that.bundleItems = (res.data && res.data.bundleItems) || []
+          // 赠品项初始化选择状态（响应式）
+          var cfgList = res.data.giftConfigs
+          if (cfgList && cfgList.length > 0) {
+            for (var gi = 0; gi < cfgList.length; gi++) {
+              var itemsArr = cfgList[gi].items || []
+              for (var gj = 0; gj < itemsArr.length; gj++) {
+                that.$set(itemsArr[gj], '_selected', false)
+              }
+            }
+          }
           that.setShareInfo(
             that.product.name,
             '/pages/discover-detail/product-detail/product-detail?id=' + that.product.id
@@ -576,16 +584,8 @@ export default {
       return item.id
     },
     toggleGift: function(item) {
-      var idx = this.selectedGiftIds.indexOf(item.id)
-      if (idx > -1) {
-        this.selectedGiftIds.splice(idx, 1)
-      } else {
-        this.selectedGiftIds.push(item.id)
-      }
-    },
-    isGiftSelected: function(item) {
-      return this.selectedGiftIds.indexOf(item.id) > -1
-    },
+      this.$set(item, '_selected', !item._selected)
+    },,
 
     onBuy: function() {
       var userId = uni.getStorageSync('userId')
@@ -611,8 +611,20 @@ export default {
         productData.specDesc = this.buildSpecDesc()
       }
       uni.setStorageSync('checkoutItems', [productData])
-      // 透传赠品选择到 checkout
-      uni.setStorageSync('checkoutGiftItemIds', this.selectedGiftIds)
+      // 透传赠品选择到 checkout（收集所有 _selected=true 的赠品项ID）
+      var selectedGiftIds = []
+      var cfgList = this.product.giftConfigs
+      if (cfgList && cfgList.length > 0) {
+        for (var gi = 0; gi < cfgList.length; gi++) {
+          var itemsArr = cfgList[gi].items || []
+          for (var gj = 0; gj < itemsArr.length; gj++) {
+            if (itemsArr[gj]._selected) {
+              selectedGiftIds.push(itemsArr[gj].id)
+            }
+          }
+        }
+      }
+      uni.setStorageSync('checkoutGiftItemIds', selectedGiftIds)
       var deliveryMethod = this.product.deliveryMethod || 1
       if (deliveryMethod > 1 && this.product.deliveryConfig) {
         productData.deliveryMethod = deliveryMethod