feat(journal task): add crud operations for task answers

重构了任务答案的处理逻辑，将原有的先删后插从任务更新中拆分出来，新增独立的答案增删改查接口：
1. 移除了JournalPageTaskUpdateInput中的TaskAnswer属性
2. 新增JournalTaskAnswerAddInput/UpdateInput DTO
3. 在服务层实现答案的增删改业务逻辑，包含OSS文件处理
4. 在控制器中添加对应的API接口

QYZH.InteractiveMagazine.WebApi/Controllers/JournalController.cs

@@ -506,6 +506,39 @@ namespace QYZH.InteractiveMagazine.WebApi.Controllers
             var data = await JournalPageTaskService.ComplementAsync(input);
             return BaseResponse<bool>.Success(data);
         }
+
+        /// <summary>
+        /// 答案新增
+        /// </summary>
+        /// <returns></returns>
+        [HttpPost, Route("page/task/answer/add")]
+        public async Task<BaseResponse<long>> AnswerAdd(JournalTaskAnswerAddInput input)
+        {
+            var data = await JournalPageTaskService.AddAnswerAsync(input);
+            return BaseResponse<long>.Success(data);
+        }
+
+        /// <summary>
+        /// 答案更新
+        /// </summary>
+        /// <returns></returns>
+        [HttpPost, Route("page/task/answer/update")]
+        public async Task<BaseResponse<bool>> AnswerUpdate(JournalTaskAnswerUpdateInput input)
+        {
+            var data = await JournalPageTaskService.UpdateAnswerAsync(input);
+            return BaseResponse<bool>.Success(data);
+        }
+
+        /// <summary>
+        /// 答案删除
+        /// </summary>
+        /// <returns></returns>
+        [HttpPost, Route("page/task/answer/delete/{id:long}")]
+        public async Task<BaseResponse<bool>> AnswerDelete(long id)
+        {
+            var data = await JournalPageTaskService.DeleteAnswerAsync(id);
+            return BaseResponse<bool>.Success(data);
+        }
         #endregion        
     }
 }