fix: remove dead code in BulkUpdateAccounts group binding loop

backend/internal/service/admin_service.go

@@ -1539,9 +1539,8 @@ func (s *adminServiceImpl) BulkUpdateAccounts(ctx context.Context, input *BulkUp
 
 	needMixedChannelCheck := input.GroupIDs != nil && !input.SkipMixedChannelCheck
 
-	// 预加载账号平台信息（混合渠道检查或 Sora 同步需要）。
+	// 预加载账号平台信息（混合渠道检查需要）。
 	platformByID := map[int64]string{}
-	groupAccountsByID := map[int64][]Account{}
 	if needMixedChannelCheck {
 		accounts, err := s.accountRepo.GetByIDs(ctx, input.AccountIDs)
 		if err != nil {
@@ -1608,7 +1607,6 @@ func (s *adminServiceImpl) BulkUpdateAccounts(ctx context.Context, input *BulkUp
 	// Handle group bindings per account (requires individual operations).
 	for _, accountID := range input.AccountIDs {
 		entry := BulkUpdateAccountResult{AccountID: accountID}
-		platform := ""
 
 		if input.GroupIDs != nil {
 			if err := s.accountRepo.BindGroups(ctx, accountID, *input.GroupIDs); err != nil {
@@ -1619,9 +1617,6 @@ func (s *adminServiceImpl) BulkUpdateAccounts(ctx context.Context, input *BulkUp
 				result.Results = append(result.Results, entry)
 				continue
 			}
-			if !input.SkipMixedChannelCheck && platform != "" {
-				updateMixedChannelPreloadedAccounts(groupAccountsByID, *input.GroupIDs, accountID, platform)
-			}
 		}
 
 		entry.Success = true