Improve authentication error handling

- Enhance error messages for authentication failures.

src/components/auth/RegisterForm.tsx

@@ -9,7 +9,7 @@ import { useToast } from "@/hooks/useToast.wrapper";
 import { verifyServerConnection } from "@/contexts/auth/auth.utils";
 
 interface RegisterFormProps {
-  signUp: (email: string, password: string, username: string) => Promise<{
+  signUp: (email: string, password: string) => Promise<{
     error: any;
     user: any;
   }>;
@@ -88,7 +88,7 @@ const RegisterForm: React.FC<RegisterFormProps> = ({
     setIsLoading(true);
     
     try {
-      const { error, user } = await signUp(email, password, username);
+      const { error, user } = await signUp(email, password);
       
       if (error) {
         setRegisterError(error.message || '알 수 없는 오류가 발생했습니다.');