Fix: Correct signUp type definition

The signUp function in AuthContextType was expecting only two arguments (email, password) but the RegisterForm component was passing three arguments (email, password, username). This commit updates the AuthContextType definition to match the actual usage in the RegisterForm component, resolving the TypeScript error.

src/components/auth/RegisterForm.tsx

@@ -1,4 +1,3 @@
-
 import React, { useState } from "react";
 import { useNavigate } from "react-router-dom";
 import { Label } from "@/components/ui/label";
@@ -9,7 +8,7 @@ import { useToast } from "@/hooks/useToast.wrapper";
 import { verifyServerConnection } from "@/contexts/auth/auth.utils";
 
 interface RegisterFormProps {
-  signUp: (email: string, password: string) => Promise<{
+  signUp: (email: string, password: string, username: string) => Promise<{
     error: any;
     user: any;
   }>;
@@ -88,7 +87,7 @@ const RegisterForm: React.FC<RegisterFormProps> = ({
     setIsLoading(true);
     
     try {
-      const { error, user } = await signUp(email, password);
+      const { error, user } = await signUp(email, password, username);
       
       if (error) {
         setRegisterError(error.message || '알 수 없는 오류가 발생했습니다.');