refactor: 로그인폼 encType attribute 추가

src/components/auth/Login.jsx

@@ -12,7 +12,7 @@ export default function Login() {
         </div>
 
         <div className="mt-10 sm:mx-auto sm:w-full sm:max-w-sm">
-          <form action={login} method="POST" className="space-y-6">
+          <form action={login} method="POST" encType="application/json" className="space-y-6">
             <div>
               <label htmlFor="userId" className="block text-sm font-medium leading-6 text-gray-900">
                 User ID