feat: 售空商品图片显示黑白效果

pages/index/index.wxml

@@ -148,7 +148,7 @@
             bindtap="viewGoodsDetail"
             wx:if="{{!item.isAd && filteredGoods.length > 0}}"
           >
-            <view class="product-card">
+            <view class="product-card {{item.status === 'sold_out' ? 'sold-out-grayscale' : ''}}">
               <view class="product-image-wrapper">
                 <!-- 视频处理：根据mediaItems中的类型字段判断 -->
                 <video 

pages/index/index.wxss

@@ -1362,6 +1362,13 @@ video.product-media {
   object-fit: fill;
 }
 
+/* 售空商品黑白效果 - 仅图片 */
+.sold-out-grayscale .product-image-wrapper .product-media,
+.sold-out-grayscale .product-image-wrapper image,
+.sold-out-grayscale .product-image-wrapper video {
+  filter: grayscale(85%);
+}
+
 /* 促销标签 */
 .promo-tag {
   position: absolute;
@@ -1393,8 +1400,32 @@ video.product-media {
 .promo-tag.sold-out {
   background: linear-gradient(135deg, #a92a2aff 0%, #a6a6a6 100%);
   box-shadow: 0 2rpx 8rpx rgba(140, 140, 140, 0.3);
-  transform: skewX(-10deg);
-  left: -20rpx;
+}
+
+/* 售空水印样式 */
+.sold-out-watermark {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: rgba(0, 0, 0, 0.4);
+  z-index: 10;
+  transform: rotate(-15deg);
+}
+
+.sold-out-text {
+  font-size: 56rpx;
+  font-weight: 700;
+  color: #fff;
+  text-shadow: 2rpx 2rpx 8rpx rgba(0, 0, 0, 0.5);
+  letter-spacing: 8rpx;
+  border: 6rpx solid rgba(255, 255, 255, 0.8);
+  padding: 16rpx 40rpx;
+  border-radius: 8rpx;
 }
 
 /* 商品信息区域 */