fix: 优化删除按钮和数量选择器样式

删除按钮：
- 改用垃圾桶图标，更直观美观
- 圆角矩形背景，hover效果
- 红色主题，符合删除语义

数量选择器：
- 增加宽度至110px
- 调整padding确保数字居中
- 加减按钮宽度32px，易于点击
- 数字居中显示，不再重叠

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/views/user/Cart.vue

@@ -51,7 +51,9 @@
                 <!-- 标题行：商品名 + 删除按钮 -->
                 <div class="item-title-row">
                   <h4 class="item-name" @click="$router.push(`/products/${item.product?.id}`)">{{ item.product?.name }}</h4>
-                  <el-button class="btn-delete" link type="danger" @click.stop="removeItem(item.id)">删除</el-button>
+                  <span class="btn-delete" @click.stop="removeItem(item.id)">
+                    <el-icon><Delete /></el-icon>
+                  </span>
                 </div>
                 <!-- 标签 -->
                 <div class="item-tags" v-if="item.product?.require_credit || item.product?.credit_reward > 0">
@@ -247,9 +249,9 @@
 import { ref, reactive, computed, watch, onMounted, markRaw } from 'vue'
 import { useRouter } from 'vue-router'
 import { ElMessage, ElMessageBox } from 'element-plus'
-import { 
+import {
   ShoppingCart, Picture, Location, CreditCard, Plus, CircleCheckFilled,
-  Wallet, Coin, ChatDotRound
+  Wallet, Coin, ChatDotRound, Delete
 } from '@element-plus/icons-vue'
 import { useCartStore } from '../../store/cart'
 import { systemApi, addressApi, orderApi, paymentChannelApi } from '../../api'
@@ -564,7 +566,7 @@ onMounted(() => {
   }
 
   /* 桌面端布局 */
-  > .item-check { width: 40px; flex-shrink: 0; }
+  > .item-check { width: 60px; flex-shrink: 0; }
   > .item-image-wrap { width: 70px; flex-shrink: 0; }
   > .item-content { flex: 1; min-width: 200px; }
   > .item-price { width: 100px; text-align: center; flex-shrink: 0; }
@@ -581,15 +583,6 @@ onMounted(() => {
   align-items: flex-start;
 }
 
-/* 移动端专用元素 - 桌面端隐藏 */
-.item-image-wrap {
-  display: none;
-}
-
-.item-content {
-  display: none;
-}
-
 .item-image {
   width: 70px;
   height: 70px;
@@ -603,6 +596,7 @@ onMounted(() => {
 .item-image-wrap {
   margin-right: 12px;
   cursor: pointer;
+  display: block;
 }
 
 .item-content {
@@ -619,9 +613,7 @@ onMounted(() => {
 }
 
 .item-bottom-row {
-  display: flex;
-  align-items: center;
-  gap: 8px;
+  display: none;
 }
 
 .btn-delete {
@@ -1130,10 +1122,25 @@ onMounted(() => {
 
   /* 删除按钮 */
   .item-content .btn-delete {
-    display: block !important;
+    display: flex !important;
+    align-items: center !important;
+    justify-content: center !important;
     flex-shrink: 0 !important;
-    font-size: 12px !important;
-    padding: 0 !important;
+    width: 28px !important;
+    height: 28px !important;
+    border-radius: 4px !important;
+    background: rgba(245, 108, 108, 0.1) !important;
+    cursor: pointer !important;
+    transition: all 0.2s !important;
+  }
+
+  .item-content .btn-delete:hover {
+    background: rgba(245, 108, 108, 0.2) !important;
+  }
+
+  .item-content .btn-delete .el-icon {
+    font-size: 14px !important;
+    color: #f56c6c !important;
   }
 
   /* 标签 */
@@ -1173,15 +1180,27 @@ onMounted(() => {
   }
 
   .item-content .quantity-wrap :deep(.el-input-number) {
-    width: 100px !important;
+    width: 110px !important;
   }
 
   .item-content .quantity-wrap :deep(.el-input-number .el-input__wrapper) {
-    padding: 0 4px !important;
+    padding: 0 38px !important;
+  }
+
+  .item-content .quantity-wrap :deep(.el-input-number__decrease) {
+    width: 32px !important;
+    left: 2px !important;
+  }
+
+  .item-content .quantity-wrap :deep(.el-input-number__increase) {
+    width: 32px !important;
+    right: 2px !important;
   }
 
   .item-content .quantity-wrap :deep(.el-input-number .el-input__inner) {
-    font-size: 13px !important;
+    font-size: 14px !important;
+    text-align: center !important;
+    padding: 0 !important;
   }
 
   /* 地址 */