重构小程序图标组件，替换传统 emoji 为 SVG 图标，提升视觉一致性和可维护性。更新多个页面以使用新图标组件，优化用户界面体验。同时，调整了数据加载逻辑，确保更高效的状态管理和用户交互。

miniprogram/pages/purchases/purchases.js

@@ -40,7 +40,7 @@ Page({
       const orders = purchasedSections.map((id, index) => ({
         id: `order_${index}`,
         sectionId: id,
-        sectionMid: app.getSectionMid(id),
+        sectionMid: 0,
         title: `章节 ${id}`,
         amount: 1,
         status: 'completed',
@@ -52,7 +52,7 @@ Page({
       const purchasedSections = app.globalData.purchasedSections || []
       this.setData({
         orders: purchasedSections.map((id, i) => ({
-          id: `order_${i}`, sectionId: id, sectionMid: app.getSectionMid(id), title: `章节 ${id}`, amount: 1, status: 'completed',
+          id: `order_${i}`, sectionId: id, sectionMid: 0, title: `章节 ${id}`, amount: 1, status: 'completed',
           createTime: new Date(Date.now() - i * 86400000).toLocaleDateString()
         }))
       })

miniprogram/pages/purchases/purchases.wxml

@@ -28,7 +28,7 @@
     </view>
 
     <view class="empty" wx:else>
-      <text class="empty-icon">📦</text>
+      <icon name="package" size="80" color="#3a3a3c" customClass="empty-icon"></icon>
       <text class="empty-text">暂无订单</text>
     </view>
   </view>