Issue Description: For a serial-managed item (A00006, ManageSerialNumbers = tYES), creating a delivery fails with "Cannot add row without complete selection of batch/serial numbers" even when the payload includes the full serial selection (SystemNumber + InternalSerialNumber + Quantity = 1 for each of 15 serials, verified to exist in SerialNumberDetails).
Variations tried: with/without serial strings, per-serial bin allocations, different SerialAndBatchNumbersBaseLine values. Additionally, querying availability via SerialNumberDetails filtered by Status eq 'rst_Available' returns HTTP 502 (origin bad gateway) on every attempt - the unfiltered query works, so the status filter appears to crash the origin server. The StockSerialNumbers entity set does not exist on this Service Layer, so there is no reliable way to determine which serials are in stock.
Expected outcome: Assistant should be able to create delivery for serial-managed items.
