fix(ERP-248): fallback subsidy from subsidies[] when getSubsidy() returns null

fix(ERP-248): fallback subsidy from subsidies[] when getSubsidy() returns null

YandexMarket deprecated the item-level `subsidy` field and stopped sending
it for some order types (DBS). Instead, subsidy is now in `subsidies[]`.

When getSubsidy() returns null:
- sum amounts from getSubsidies() array
- log Yii::warning with calculated value

When getPartnerWarehouseId() returns null:
- fall back to marketplace_order.warehouse_guid (valid for DBS orders)
- only Yii::error if warehouse_guid is also null

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>