refactor: 统一业务异常处理，标准化结果码和错误响应

1.  新增并完善ResultCode枚举，补充标准HTTP状态码对应的业务状态码
2.  重构BusinessException，新增基于ResultCode的构造函数和ThrowIf扩展方法
3.  替换所有硬编码的HTTP状态码为统一的ResultCode枚举
4.  优化全局异常中间件，根据业务状态码映射对应HTTP状态码并规范化JSON响应
5.  修复OssImageHelper和AutoDotCodeConsumer中的OSS文件处理逻辑
6.  新增用户答题快照实体类
7.  清理废弃的宠物模块迁移脚本

QYZH.InteractiveMagazine.WebApi/Controllers/JournalController.cs

@@ -395,15 +395,15 @@ namespace QYZH.InteractiveMagazine.WebApi.Controllers
         {
             var entity = await JournalService.GetFirstAsync(x => x.Id == JournalId);
             if (entity == null)
-                throw new BusinessException("书籍不存在");
+                throw new BusinessException("书籍不存在", ResultCode.NOT_FOUND);
 
             var downloadUrl = entity.DownloadJournalPagePdfName;
             if (string.IsNullOrWhiteSpace(downloadUrl))
-                throw new BusinessException("下载点阵码PDF文件为空,请先铺码");
+                throw new BusinessException("下载点阵码PDF文件为空,请先铺码", ResultCode.BAD_REQUEST);
 
             var stream = await httpClientFactory.CreateClient().GetStreamAsync(downloadUrl);  //创建文件流
             if (stream == null)
-                throw new BusinessException("下载点阵码PDF文件失败");
+                throw new BusinessException("下载点阵码PDF文件失败", ResultCode.GLOBAL_ERROR);
 
             Response.Headers.Append("Access-Control-Expose-Headers", "Content-Disposition");