rework configuration save, load configuration backups when available and config cannot be read

fix unnecessary config reload on save

MareSynchronos/UI/SyncshellAdminUI.cs

@@ -351,7 +351,7 @@ public class SyncshellAdminUI : WindowMediatorSubscriberBase
                             using var pushId = ImRaii.PushId(bannedUser.UID);
                             if (_uiSharedService.IconTextButton(FontAwesomeIcon.Check, "Unban"))
                             {
-                                _ = _apiController.GroupUnbanUser(bannedUser);
+                                _apiController.GroupUnbanUser(bannedUser);
                                 _bannedUsers.RemoveAll(b => string.Equals(b.UID, bannedUser.UID, StringComparison.Ordinal));
                             }
                         }