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.Models/Dto/Journal/JournalPageTaskUpdateInput.cs

@@ -37,11 +37,6 @@ namespace QYZH.InteractiveMagazine.Models.Dto.Journal
         /// </summary>
         public string Task { get; set; }
 
-        /// <summary>
-        /// 答案
-        /// </summary>
-        public List<JournalTaskAnswerInput> TaskAnswer { get; set; }
-
         /// <summary>
         /// 积分
         /// </summary>

QYZH.InteractiveMagazine.Models/Dto/Journal/JournalTaskAnswerAddInput.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace QYZH.InteractiveMagazine.Models.Dto.Journal
+{
+    public class JournalTaskAnswerAddInput
+    {
+        /// <summary>
+        /// 题目Id
+        /// </summary>
+        public long JournalPageTaskId { get; set; }
+
+        /// <summary>
+        /// 参考答案
+        /// </summary>
+        public string Answer { get; set; }
+
+        /// <summary>
+        /// 参考答案图片
+        /// </summary>
+        public string AnswerUrl { get; set; }
+    }
+}

QYZH.InteractiveMagazine.Models/Dto/Journal/JournalTaskAnswerUpdateInput.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace QYZH.InteractiveMagazine.Models.Dto.Journal
+{
+    public class JournalTaskAnswerUpdateInput
+    {
+        /// <summary>
+        /// 答案Id
+        /// </summary>
+        public long Id { get; set; }
+
+        /// <summary>
+        /// 参考答案
+        /// </summary>
+        public string Answer { get; set; }
+
+        /// <summary>
+        /// 参考答案图片
+        /// </summary>
+        public string AnswerUrl { get; set; }
+    }
+}