🐛 fix: 닉네임 수정 로직에 닉네임 관련 예외처리 추가

Author: jiwon1217

backend/src/main/java/io/f1/backend/domain/user/app/UserService.java

@@ -98,6 +98,8 @@ public void deleteUser(Long userId) {
 
     @Transactional
     public void updateNickname(Long userId, String newNickname, HttpSession session) {
+        checkNickname(newNickname);
+
         User user = initNickname(userId, newNickname);
         session.setAttribute(USER, AuthenticationUser.from(user));
         SecurityUtils.setAuthentication(user);