让换货选择不受新资产状态与原归属阻碍

新资产仍需通过有效客户绑定和进行中换货占用校验，并返回明确的绑定冲突提示。

Constraint: 运营明确要求移除新资产在库和店铺一致限制

Rejected: 保留在库条件仅放宽店铺归属 | 无法支持已销售资产参与换货

Confidence: high

Scope-risk: moderate

Directive: 不得移除客户绑定和换货占用校验

Tested: git diff --check

Not-tested: 按用户要求未运行自动化测试

internal/service/exchange/service.go

@@ -801,14 +801,6 @@ func (s *Service) validateExchangeAssetsWithTx(ctx context.Context, tx *gorm.DB,
 	if !isExchangeableAssetStatus(oldAsset.AssetStatus) {
 		return oldAssetStatusError(oldAsset.AssetStatus)
 	}
-	if newAsset.AssetStatus != constants.AssetStatusInStock {
-		return errors.New(errors.CodeExchangeNewAssetNotInStock)
-	}
-	// 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 {
 		return err
 	}
@@ -835,7 +827,7 @@ func (s *Service) ensureNewAssetBindingAvailableWithTx(ctx context.Context, tx *
 		return errors.Wrap(errors.CodeDatabaseError, err, "查询新资产客户绑定失败")
 	}
 	if newBindCount > 0 {
-		return errors.New(errors.CodeExchangeStatusInvalid, "新资产已存在有效客户绑定")
+		return errors.New(errors.CodeExchangeStatusInvalid, "新资产存在有效客户绑定，不可用于换货")
 	}
 	return nil
 }
@@ -862,7 +854,7 @@ func (s *Service) syncNewAssetOwnershipWithTx(ctx context.Context, tx *gorm.DB,
 	}
 
 	result := tx.WithContext(ctx).Model(modelValue).
-		Where("id = ? AND asset_status = ?", newAsset.AssetID, constants.AssetStatusInStock).
+		Where("id = ?", newAsset.AssetID).
 		Updates(map[string]any{
 			"shop_id":    oldAsset.ShopID,
 			"status":     ownershipStatus,
@@ -872,7 +864,7 @@ func (s *Service) syncNewAssetOwnershipWithTx(ctx context.Context, tx *gorm.DB,
 		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)
+		return errors.New(errors.CodeAssetNotFound)
 	}
 
 	shopIDTag := uint(0)
@@ -910,13 +902,13 @@ func (s *Service) updateAssetStatusesForCompletion(ctx context.Context, tx *gorm
 			return errors.New(errors.CodeExchangeStatusInvalid, "旧资产状态已被修改，请重试")
 		}
 		result = tx.WithContext(ctx).Model(&model.IotCard{}).
-			Where("id = ? AND asset_status = ?", newAsset.AssetID, constants.AssetStatusInStock).
+			Where("id = ?", newAsset.AssetID).
 			Updates(map[string]any{"asset_status": constants.AssetStatusSold, "updated_at": now})
 		if result.Error != nil {
 			return errors.Wrap(errors.CodeDatabaseError, result.Error, "更新新卡状态失败")
 		}
 		if result.RowsAffected == 0 {
-			return errors.New(errors.CodeExchangeNewAssetNotInStock)
+			return errors.New(errors.CodeAssetNotFound)
 		}
 		return nil
 	}
@@ -930,13 +922,13 @@ func (s *Service) updateAssetStatusesForCompletion(ctx context.Context, tx *gorm
 		return errors.New(errors.CodeExchangeStatusInvalid, "旧资产状态已被修改，请重试")
 	}
 	result = tx.WithContext(ctx).Model(&model.Device{}).
-		Where("id = ? AND asset_status = ?", newAsset.AssetID, constants.AssetStatusInStock).
+		Where("id = ?", newAsset.AssetID).
 		Updates(map[string]any{"asset_status": constants.AssetStatusSold, "updated_at": now})
 	if result.Error != nil {
 		return errors.Wrap(errors.CodeDatabaseError, result.Error, "更新新设备状态失败")
 	}
 	if result.RowsAffected == 0 {
-		return errors.New(errors.CodeExchangeNewAssetNotInStock)
+		return errors.New(errors.CodeAssetNotFound)
 	}
 	return nil
 }
@@ -1007,13 +999,6 @@ func preferredDeviceIdentifier(device *model.Device) string {
 	return device.SN
 }
 
-func sameShopID(left, right *uint) bool {
-	if left == nil || right == nil {
-		return left == nil && right == nil
-	}
-	return *left == *right
-}
-
 func (s *Service) toExchangeOrderResponse(order *model.ExchangeOrder) *dto.ExchangeOrderResponse {
 	if order == nil {
 		return nil