feat(orderConfirm): 优化订单确认页面功能和样式

- 添加优惠券选择功能
- 增加商品数量选择
- 完善订单信息展示
- 优化支付流程
- 添加错误状态和加载状态处理
- 新增 OrderConfirmSkeleton 组件用于加载骨架屏

src/shop/orderConfirm/index.scss

@@ -1,6 +1,21 @@
 .order-confirm-page {
   padding-bottom: 100px; // 留出底部固定按钮的空间
 
+  .error-state {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    padding: 60px 20px;
+    text-align: center;
+
+    .error-text {
+      color: #999;
+      margin-bottom: 20px;
+      font-size: 14px;
+    }
+  }
+
   .fixed-bottom {
     position: fixed;
     bottom: 0;
@@ -42,3 +57,51 @@
     content: "";
   }
 }
+
+// 优惠券弹窗样式
+.coupon-popup {
+  height: 100%;
+  display: flex;
+  flex-direction: column;
+
+  &__header {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    padding: 16px;
+    border-bottom: 1px solid #f0f0f0;
+  }
+
+  &__title {
+    font-size: 16px;
+    font-weight: 600;
+    color: #333;
+  }
+
+  &__content {
+    flex: 1;
+    overflow-y: auto;
+  }
+
+  &__current {
+    padding: 16px;
+    background: #f8f9fa;
+    border-bottom: 1px solid #f0f0f0;
+
+    &-title {
+      font-size: 14px;
+      color: #666;
+      margin-bottom: 8px;
+    }
+
+    &-item {
+      display: flex;
+      justify-content: space-between;
+      align-items: center;
+      padding: 8px 12px;
+      background: #fff;
+      border-radius: 6px;
+      font-size: 14px;
+    }
+  }
+}