feat(shop): 使用白色购物车图标替换文本图标

- 引入了 base64 格式的白色购物车 SVG 图标常量
- 将购物车按钮内的文本符号替换为可自适应大小的 Image 组件
- 保持图标外观和布局一致，增强视觉统一性
- 提升图标加载性能，适配绿色浮动按钮主题

src/pages/shop/index.tsx

@@ -14,6 +14,7 @@ import { useShare } from '@/hooks/useShare'
 import EmptyState from '@/components/common/EmptyState'
 import LoadMore from '@/components/common/LoadMore'
 import Price from '@/components/common/Price'
+import { CART_ICON_WHITE } from '@/assets/icons'
 
 definePageConfig({
   navigationBarTitleText: '商品分类',
@@ -360,7 +361,11 @@ const ShopPage: React.FC = () => {
         }}
         onClick={() => Taro.navigateTo({ url: '/pages/shop/cart' })}
       >
-        <Text className='text-white text-xl'>🛒</Text>
+        <Image
+          className='w-7 h-7'
+          src={CART_ICON_WHITE}
+          mode='aspectFit'
+        />
         {totalCount > 0 && (
           <View
             className='flex items-center justify-center'