feat: implement AuthModule with authentication and RBAC features

Added AuthModule with services, controllers, and guards for authentication. Implements session management, role-based access control, 2FA, and DTOs for user login, registration, and token refresh.

backend/src/auth/dto/register.dto.ts

@@ -0,0 +1,14 @@
+import { IsEmail, IsNotEmpty, IsString, MinLength } from "class-validator";
+
+export class RegisterDto {
+	@IsString()
+	@IsNotEmpty()
+	username!: string;
+
+	@IsEmail()
+	email!: string;
+
+	@IsString()
+	@MinLength(8)
+	password!: string;
+}