fix(shop): 修复商品详情页孤立“0”渲染问题

- 修正赚取积分、重量和销量条件渲染，避免数字0被渲染成文本节点
- 赚取积分判断改为仅判断数值是否大于0，防止0泄漏
- 重量同样改为判断数值大于0避免显示无效数据
- 销量为0时隐藏销量信息，符合用户需求
- 调整加购按钮尺寸，使其视觉更协调

src/pages/shop/category.tsx

@@ -262,7 +262,7 @@ const CategoryPage: React.FC = () => {
                         </View>
                         {/* 加购按钮 */}
                         <View
-                          className='w-7 h-7 rounded-full bg-green-500 flex items-center justify-center flex-shrink-0'
+                          className='w-6 h-6 rounded-full bg-green-500 flex items-center justify-center flex-shrink-0'
                           onClick={(e) => handleAddToCart(e, item)}
                         >
                           <Text className='text-white text-lg leading-none'>+</Text>

src/pages/shop/product-detail.tsx

@@ -309,13 +309,15 @@ const ProductDetailPage: React.FC = () => {
             </View>
           )}
           {/* 赚取积分 */}
-          {product.gainIntegral && Number(product.gainIntegral) > 0 && (
+          {Number(product.gainIntegral) > 0 && (
             <View className='mt-1'>
               <Text className='text-xs text-orange-500'>购买可得 {product.gainIntegral} 积分</Text>
             </View>
           )}
           <View className='flex gap-2 mt-2'>
-            <Text className='text-xs text-gray-400'>销量: {product.sales || 0}</Text>
+            {Number(product.sales) > 0 && (
+              <Text className='text-xs text-gray-400'>销量: {product.sales}</Text>
+            )}
             <Text className='text-xs text-gray-400'>库存: {product.stock || 0}</Text>
             {product.unitName && (
               <Text className='text-xs text-gray-400'>单位: {product.unitName}</Text>
@@ -363,7 +365,7 @@ const ProductDetailPage: React.FC = () => {
           <View className='flex items-center'>
             <Text className='text-xs text-gray-500 mr-2'>配送</Text>
             <Text className='text-sm text-gray-700'>{deliveryText}</Text>
-            {product.goodsWeight && Number(product.goodsWeight) > 0 && (
+            {Number(product.goodsWeight) > 0 && (
               <Text className='text-xs text-gray-400 ml-2'>重量: {product.goodsWeight}kg</Text>
             )}
           </View>