feat: 申诉常见理由快捷选择 + 证据截图上传

- 后端: 新增 appeal_reason_type, appeal_evidence_urls 字段
- 后端: 新建 upload_routes.py 图片上传接口
- 前端: history 页面添加快捷理由选择器 + 截图上传
- 前端: admin-review 页面展示证据图片 + 点击预览
- 新增 SQL 更新脚本 update_appeal_fields.sql

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

miniprogram/pages/admin-review/index.wxml

@@ -100,9 +100,19 @@
       <view class="list-item" wx:for="{{appeals}}" wx:key="id">
         <view class="item-title">{{item.text}}</view>
         <view class="item-sub">申诉人：{{item.nickname || item.username}} · 当前状态：{{item.appeal_status_text}}</view>
+        <view class="item-sub">申诉理由类型：{{item.appeal_reason_type || '未选择'}}</view>
         <view class="item-sub">申诉理由：{{item.appeal_reason || '未填写'}}</view>
         <view class="item-sub">时间：{{item.created_text}}</view>
 
+        <view class="field" wx:if="{{item.appeal_evidence_urls && item.appeal_evidence_urls.length}}">
+          <text class="field-label">证据截图</text>
+          <view class="evidence-grid">
+            <view class="evidence-item" wx:for="{{item.appeal_evidence_urls}}" wx:for-item="evidenceUrl" wx:key="*this">
+              <image class="evidence-thumb evidence-clickable" src="{{evidenceUrl}}" mode="aspectFill" data-url="{{evidenceUrl}}" bindtap="previewEvidence" />
+            </view>
+          </view>
+        </view>
+
         <textarea class="textarea note-textarea" placeholder="可填写申诉处理备注" value="{{appealNoteMap[item.id] || ''}}" data-id="{{item.id}}" bindinput="onAppealNoteInput" />
 
         <view class="btn-row">