fix

Application/TransactionCategoryApplication.cs

@@ -17,6 +17,7 @@ public interface ITransactionCategoryApplication
     Task<int> BatchCreateAsync(List<CreateCategoryRequest> requests);
     Task<string> GenerateIconAsync(GenerateIconRequest request);
     Task UpdateSelectedIconAsync(UpdateSelectedIconRequest request);
+    Task DeleteIconAsync(long classificationId);
 }
 
 /// <summary>
@@ -215,6 +216,25 @@ public class TransactionCategoryApplication(
         }
     }
 
+    public async Task DeleteIconAsync(long classificationId)
+    {
+        var category = await categoryRepository.GetByIdAsync(classificationId);
+        if (category == null)
+        {
+            throw new NotFoundException("分类不存在");
+        }
+
+        // 将 Icon 字段设置为 null
+        category.Icon = null;
+        category.UpdateTime = DateTime.Now;
+
+        var success = await categoryRepository.UpdateAsync(category);
+        if (!success)
+        {
+            throw new BusinessException("删除图标失败");
+        }
+    }
+
     private static CategoryResponse MapToResponse(TransactionCategory category)
     {
         return new CategoryResponse