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.Infrastructure/OSS/OssImageHelper.cs

@@ -1,6 +1,7 @@
 using Microsoft.Extensions.Logging;
 using QYZH.InteractiveMagazine.Common.Extensions;
 using QYZH.InteractiveMagazine.Models.Common;
+using QYZH.InteractiveMagazine.Models.Dto;
 
 namespace QYZH.InteractiveMagazine.Infrastructure.OSS;
 
@@ -87,7 +88,7 @@ public class OssImageHelper
         catch (Exception ex) when (ex is not BusinessException)
         {
             _logger.LogError(ex, "OSS 图片搬运异常，Source: {Source}, Target: {Target}", sourcePath, targetPath);
-            throw new BusinessException("图片搬运失败，请重试", 500);
+            throw new BusinessException("图片搬运失败，请重试", ResultCode.GLOBAL_ERROR);
         }
     }
 

QYZH.InteractiveMagazine.Infrastructure/OSS/OssService.cs

@@ -7,6 +7,8 @@ using CSRedis;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using QYZH.InteractiveMagazine.Common.Extensions;
+using QYZH.InteractiveMagazine.Models.Common;
+using QYZH.InteractiveMagazine.Models.Dto;
 using System.Text.Json;
 using System.Web;
 
@@ -193,6 +195,53 @@ namespace QYZH.InteractiveMagazine.Infrastructure.OSS
             }
         }
 
+        /// <summary>
+        /// 判断对象是否存在
+        /// </summary>
+        /// <param name="key"></param>
+        /// <returns></returns>
+        public bool DoesObjectExist(string key)
+        {
+            try
+            {
+                if (key.IsNull()) return false;
+
+                key = key.RemoveDomain();
+                key = HttpUtility.UrlDecode(key);
+
+                return _ossClient.DoesObjectExist(_ossOption.BucketName, key);
+            }
+            catch (OssException ex)
+            {
+                _logger.LogError(ex.Message + ex.StackTrace);
+                return false;
+            }
+        }
+
+        /// <summary>
+        /// 获取对象内容流
+        /// </summary>
+        /// <param name="key"></param>
+        /// <returns></returns>
+        public Stream? GetObjectStream(string key)
+        {
+            try
+            {
+                if (key.IsNull()) return null;
+
+                key = key.RemoveDomain();
+                key = HttpUtility.UrlDecode(key);
+
+                var ossObject = _ossClient.GetObject(_ossOption.BucketName, key);
+                return ossObject.Content;
+            }
+            catch (OssException ex)
+            {
+                _logger.LogError(ex.Message + ex.StackTrace);
+                return null;
+            }
+        }
+
         /// <summary>
         /// 删除多个
         /// </summary>