refactor: replace border-box with box-border and clean up unused scss

Remove the unused box-sizing.scss stylesheet and its import from the main SCSS index file.
Update all Vue component template class references from the custom border-box class to the
native box-border utility class to eliminate redundant custom CSS and align with the project's
utility class conventions.

src/pages-order/order/components/OrderCard/OrderCardContent.vue

@@ -1,5 +1,5 @@
 <template>
-  <view class="card-content border-box pt-[12px]">
+  <view class="card-content box-border pt-[12px]">
     <view class="flex items-center justify-between">
       <view class="left flex-full font-size-14 line-height-20 color-171717 mr-12">
         {{ orderData.commodityName }}

src/pages-order/order/components/OrderCard/index.vue

@@ -1,5 +1,5 @@
 <template>
-  <view class="order-card bg-white border-box p-[12px] rounded-12 m-12" @click.stop="handleCardClick">
+  <view class="order-card bg-white box-border p-[12px] rounded-12 m-12" @click.stop="handleCardClick">
     <!-- 卡片头部 -->
     <view class="card-header flex items-center">
       <view class="status-info flex items-center flex-full">
@@ -21,7 +21,7 @@
 
     <view v-if="orderData.orderStatus === '0'" class="text-right">
       <button
-        class="go-pay border-box border-none font-size-14 color-white bg-[#ff3d60] rounded-5 inline-block text-center line-height-30"
+        class="go-pay box-border border-none font-size-14 color-white bg-[#ff3d60] rounded-5 inline-block text-center line-height-30"
         @click.stop="handleCardClick">
         去支付
       </button>