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/app.wxss

@@ -399,6 +399,67 @@ button.btn::after {
   color: #ffdce1;
 }
 
+.evidence-grid {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 12rpx;
+  margin-top: 12rpx;
+}
+
+.evidence-item {
+  position: relative;
+  width: 120rpx;
+  height: 120rpx;
+  border-radius: 12rpx;
+  overflow: hidden;
+  border: 1rpx solid rgba(139, 177, 223, 0.3);
+}
+
+.evidence-thumb {
+  width: 100%;
+  height: 100%;
+  display: block;
+}
+
+.evidence-clickable {
+  cursor: pointer;
+  transition: opacity 0.2s;
+}
+
+.evidence-clickable:active {
+  opacity: 0.8;
+}
+
+.evidence-remove {
+  position: absolute;
+  top: -4rpx;
+  right: -4rpx;
+  width: 32rpx;
+  height: 32rpx;
+  border-radius: 50%;
+  background: rgba(255, 91, 111, 0.9);
+  color: #fff;
+  font-size: 24rpx;
+  text-align: center;
+  line-height: 32rpx;
+}
+
+.evidence-add {
+  width: 120rpx;
+  height: 120rpx;
+  border-radius: 12rpx;
+  border: 1rpx dashed rgba(139, 177, 223, 0.5);
+  background: rgba(17, 35, 58, 0.5);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.evidence-add-icon {
+  font-size: 48rpx;
+  color: var(--sub);
+}
+
 .chip-group {
   display: flex;
   flex-wrap: wrap;