refactor: 完成文件模块优化重构

Yi.Abp.Net8/framework/Yi.Framework.Core/Enums/FileTypeEnum.cs

@@ -11,10 +11,10 @@ namespace Yi.Framework.Core.Enums
     /// </summary>
     public enum FileTypeEnum
     {
-        File,
-        Image,
-        Thumbnail,
-        Excel,
-        Temp
+        file,
+        image,
+        thumbnail,
+        excel,
+        temp
     }
 }

Yi.Abp.Net8/framework/Yi.Framework.Core/Helper/MimeHelper.cs

@@ -45,8 +45,8 @@ namespace Yi.Framework.Core.Helper
         {
             var extension = Path.GetExtension(fileName);
             if (ImageType.Contains(extension.ToLower()))
-                return FileTypeEnum.Image;
-            return FileTypeEnum.File;
+                return FileTypeEnum.image;
+            return FileTypeEnum.file;
 
 
         }