style(@vben/web-antd): erp-优化采购订单表单样式

- 更新 Tab 卡片样式，使用 border 和 bg-card 类
- 修改合计行样式，使用 rounded、border、bg-muted 和 text-muted-foreground 类
- 调整字体颜色，使用 text-foreground 类

apps/web-antd/src/views/erp/purchase/order/modules/PurchaseOrderItemForm.vue

@@ -232,9 +232,9 @@ defineExpose({ validate, getData, init });
 
     <template #bottom>
       <!-- 合计行 -->
-      <div class="mt-2 border bg-gray-50 p-2">
-        <div class="flex justify-between text-sm">
-          <span class="font-medium">合计：</span>
+      <div class="border-border bg-muted mt-2 rounded border p-2">
+        <div class="text-muted-foreground flex justify-between text-sm">
+          <span class="text-foreground font-medium">合计：</span>
           <div class="flex space-x-4">
             <span>数量：{{ getSummaries().count }}</span>
             <span>金额：{{ getSummaries().totalProductPrice }}</span>

apps/web-antd/src/views/erp/purchase/order/modules/form.vue

@@ -136,7 +136,7 @@ defineExpose({ modalApi });
     <Form />
 
     <!-- Tab卡片 -->
-    <div class="mt-4 rounded-lg border border-gray-200 p-2">
+    <div class="border-border bg-card mt-4 rounded-lg border p-2">
       <a-tabs default-active-key="1">
         <a-tab-pane key="1" tab="订单产品清单">
           <div class="p-4">