允许平台库存资产直接完成换货归属继承

换货完成事务允许平台库存新资产换入，并同步店铺归属、分销状态及钱包租户标签；其他店铺资产继续拒绝。

Constraint: 七月迭代要求归属继承不受 migrate_data 控制

Rejected: 先将新资产人工分配到旧资产店铺 | 会保留冲突校验并增加多余操作

Confidence: high

Scope-risk: narrow

Directive: 后续换货资料迁移不得覆盖归属继承规则

Tested: gofmt；git diff --check

Not-tested: 按用户要求未运行自动化测试

internal/service/exchange/service.go

@@ -583,6 +583,9 @@ func (s *Service) completeExchangeWithTx(ctx context.Context, tx *gorm.DB, order
 	if err = s.validateExchangeAssetsWithTx(ctx, tx, order.ID, oldAsset, newAsset); err != nil {
 		return err
 	}
+	if err = s.syncNewAssetOwnershipWithTx(ctx, tx, oldAsset, newAsset); err != nil {
+		return err
+	}
 	if err = s.switchCustomerBindingWithTx(ctx, tx, oldAsset, newAsset); err != nil {
 		return err
 	}
@@ -755,7 +758,9 @@ func (s *Service) validateExchangeAssetsWithTx(ctx context.Context, tx *gorm.DB,
 	if newAsset.AssetStatus != constants.AssetStatusInStock {
 		return errors.New(errors.CodeExchangeNewAssetNotInStock)
 	}
-	if !sameShopID(oldAsset.ShopID, newAsset.ShopID) {
+	// 平台库存资产没有店铺归属，换货完成时会继承旧资产店铺；
+	// 已归属其他店铺的资产仍必须拒绝，避免跨店铺覆盖资产归属。
+	if newAsset.ShopID != nil && !sameShopID(oldAsset.ShopID, newAsset.ShopID) {
 		return errors.New(errors.CodeForbidden, "新旧资产归属不一致")
 	}
 	if err := s.ensureNewAssetBindingAvailableWithTx(ctx, tx, oldAsset, newAsset); err != nil {
@@ -793,6 +798,59 @@ func (s *Service) switchCustomerBindingWithTx(ctx context.Context, tx *gorm.DB,
 	return s.customerBinding.Migrate(ctx, tx, oldAsset.AssetType, oldAsset.AssetID, newAsset.AssetType, newAsset.AssetID)
 }
 
+// syncNewAssetOwnershipWithTx 将新资产归属同步为旧资产当前归属。
+// 归属继承不受 migrate_data 控制，避免平台库存资产换入店铺后仍处于平台租户范围。
+func (s *Service) syncNewAssetOwnershipWithTx(ctx context.Context, tx *gorm.DB, oldAsset, newAsset *resolvedExchangeAsset) error {
+	ownershipStatus := constants.IotCardStatusInStock
+	if oldAsset.ShopID != nil {
+		ownershipStatus = constants.IotCardStatusDistributed
+	}
+
+	modelValue := any(&model.IotCard{})
+	if newAsset.AssetType == constants.ExchangeAssetTypeDevice {
+		modelValue = &model.Device{}
+		ownershipStatus = constants.DeviceStatusInStock
+		if oldAsset.ShopID != nil {
+			ownershipStatus = constants.DeviceStatusDistributed
+		}
+	}
+
+	result := tx.WithContext(ctx).Model(modelValue).
+		Where("id = ? AND asset_status = ?", newAsset.AssetID, constants.AssetStatusInStock).
+		Updates(map[string]any{
+			"shop_id":    oldAsset.ShopID,
+			"status":     ownershipStatus,
+			"updated_at": time.Now(),
+		})
+	if result.Error != nil {
+		return errors.Wrap(errors.CodeDatabaseError, result.Error, "同步新资产店铺归属失败")
+	}
+	if result.RowsAffected == 0 {
+		return errors.New(errors.CodeExchangeNewAssetNotInStock)
+	}
+
+	shopIDTag := uint(0)
+	if oldAsset.ShopID != nil {
+		shopIDTag = *oldAsset.ShopID
+	}
+	if err := tx.WithContext(ctx).Model(&model.AssetWallet{}).
+		Where("resource_type = ? AND resource_id = ?", newAsset.AssetType, newAsset.AssetID).
+		Updates(map[string]any{"shop_id_tag": shopIDTag, "updated_at": time.Now()}).Error; err != nil {
+		return errors.Wrap(errors.CodeDatabaseError, err, "同步新资产钱包店铺标签失败")
+	}
+
+	newAsset.ShopID = cloneShopID(oldAsset.ShopID)
+	return nil
+}
+
+func cloneShopID(shopID *uint) *uint {
+	if shopID == nil {
+		return nil
+	}
+	value := *shopID
+	return &value
+}
+
 func (s *Service) updateAssetStatusesForCompletion(ctx context.Context, tx *gorm.DB, oldAsset, newAsset *resolvedExchangeAsset) error {
 	now := time.Now()
 	if oldAsset.AssetType == constants.ExchangeAssetTypeIotCard {