User already exists message is red. Modals to the viewport center. Fixed Quit option: it deletes the session.

components/Profile.tsx

@@ -490,7 +490,7 @@ const Profile: React.FC<ProfileProps> = ({ user, onLogout, lang, onLanguageChang
                             <button onClick={handleCreateUser} className="w-full py-2 bg-primary text-on-primary rounded-full text-sm font-medium">
                                 {t('create_btn', lang)}
                             </button>
-                            {createMsg && <p className="text-xs text-on-surface-variant text-center">{createMsg}</p>}
+                            {createMsg && <p className="text-xs text-error text-center font-medium">{createMsg}</p>}
                         </div>
 
                         {/* User List */}