重构项目结构，移除Assignment相关功能，优化Submission模块

Entities/DTO/Authentication/AuthResponseDto.cs

@@ -0,0 +1,12 @@
+namespace Entities.DTO
+{
+    public class AuthResponseDto
+	{
+		public bool IsAuthSuccessful { get; set; }
+		public string? ErrorMessage { get; set; }
+		public string? Token { get; set; }
+		public string? RefreshToken { get; set; }
+		public bool Is2StepVerificationRequired { get; set; }	
+		public string Provider { get; set; }	
+	}
+}