fix(invitation): 邀请返利改用实际结算利润并修正提号基准

backend/internal/modules/invitation/repository.go

@@ -369,6 +369,14 @@ func (r *Repository) processOrderInvitationRebate(ctx context.Context, tx *gorm.
 	orderGrossProfitCent := order.RentAmountCent - order.OwnerRentAmountCent
 	if opts.GrossProfitCent != nil {
 		orderGrossProfitCent = *opts.GrossProfitCent
+	} else {
+		// 正常结账、仲裁等终态都已落定实际结账单；未显式传基数时优先按实际平台利润，
+		// 避免再次用订单创建时的预收毛利快照给零消耗结账发返利。
+		var committedCheckout model.OrderCheckout
+		if err := tx.Where("order_id = ? AND status IN ?", order.ID, []string{"accepted", "settled"}).
+			Order("id DESC").First(&committedCheckout).Error; err == nil {
+			orderGrossProfitCent = committedCheckout.PlatformFeeCent
+		}
 	}
 	if orderGrossProfitCent <= 0 {
 		return nil