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/dispute/arbitration.go

@@ -131,8 +131,8 @@ func (r *Repository) Arbitrate(ctx context.Context, adminID uint64, id uint64, r
 		if err := tx.Save(&order).Error; err != nil {
 			return err
 		}
-		if order.Status == "completed" {
-			if err := distribution.EnsureCompletedReleaseAtTx(tx, order.ID); err != nil {
+		if order.DistributionSiteID != nil && *order.DistributionSiteID > 0 {
+			if err := distribution.ApplyRefundTx(tx, order.ID, settlement.RenterRefundAmountCent); err != nil {
 				return err
 			}
 		}
@@ -373,6 +373,7 @@ func applyArbitrationActualSettlement(order *model.RentalOrder, checkout *model.
 	checkout.OwnerIncomeAmountCent = settlement.OwnerIncomeCent
 	checkout.ShortfallCent = settlement.ShortfallCent
 	checkout.OvershootAmountCent = settlement.OvershootAmountCent
+	checkout.Status = "settled"
 }
 
 func isPlatformManagedOrder(order model.RentalOrder) bool {