fix:solve conflict

Author: seungwookc97

src/main/java/com/back/global/security/CustomOAuth2LoginSuccessHandler.java

@@ -26,6 +26,10 @@ public void onAuthenticationSuccess(HttpServletRequest request, HttpServletRespo
         SecurityUser securityUser = (SecurityUser) authentication.getPrincipal();
         // Access Token과 Refresh Token 발급
         userAuthService.issueTokens(response, securityUser.getId(), securityUser.getEmail(), securityUser.getNickname());
-        response.sendRedirect(frontendUrl);
+
+        // 프론트엔드로 리다이렉트
+        String redirectUrl = frontendUrl;
+
+        response.sendRedirect(redirectUrl);
     }
 }