Empties had no way onto a departure: the return record could name a train
but nothing seated it on a wagon. Export schedules now expose a loading
action that packs selected returns onto free wagons at one 40ft or two 20ft
each, enforced both in the picker and in the API (existing empties on the
schedule count against their wagon).
Adds container_size, train_schedule_id and wagon_sequence_no to
freight.empty_container_returns.
The sheet attests EDR has taken custody. Export custody happens at
warehouse receipt, so the shared received-with-GRN gate now runs even
when wagons are already allocated. Receipt-row query also accepts the
legacy notes GRN fallback, matching the loading gate.
Top Returned Containers table ignored the EDR/Customer tab because
the backend never persisted which truck type performed the return.
Added returned_by column + DTO/entity field, wired create payload to
send it, and filtered the table by the active tab.
