feat(distribution): 补齐退款加价回退、本站自卖与开通默认规则

退款时压缩卖方加价，人工/自动批次仅完结单可入账，号主收入进主站钱包；仲裁后重算释放并支持作废未入账 DS。开通时四种模式按默认生效，对外口径合并为 35/40/25，不再单独展示通道费。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/internal/modules/distribution/service.go

@@ -177,6 +177,12 @@ func (s *Service) MarkSettlementBatch(ctx context.Context, adminID, id uint64) (
 	}
 	return s.repo.MarkSettlementBatch(ctx, adminID, id)
 }
+func (s *Service) CancelSettlementBatch(ctx context.Context, adminID, id uint64) (*SettlementBatchDTO, error) {
+	if err := s.available(); err != nil {
+		return nil, err
+	}
+	return s.repo.CancelSettlementBatch(ctx, adminID, id)
+}
 
 func (s *Service) CreateFinancialSnapshot(ctx context.Context, adminID, orderID uint64, req CreateFinancialSnapshotRequest) (*DistributionOrderDTO, error) {
 	if err := s.available(); err != nil {