refactor: remove custom font-weight scss and update class usages

Delete the standalone font-weight.scss utility file, remove its import from the main scss index, and update all existing references to the custom font-{weight} classes to use either built-in semantic font utilities or inline functional font weight classes matching the project's utility-first styling pattern.

src/components/SwipeCards/index.vue

@@ -13,7 +13,7 @@
         <!-- 底部：价格 + 购买按钮 -->
         <view class="card-footer p-[12px] flex flex-justify-between flex-items-center">
           <view class="border-box">
-            <view class="font-size-14 font-500 text-[#333333] ellipsis-1">
+            <view class="font-size-14 font-[500] text-[#333333] ellipsis-1">
               {{ card.commodityName }}
             </view>
             <view class="card-price-row text-[#333333]">