Direct truck-to-train export cargo skips the warehouse, so the existing
carriage acceptance sheet ready notice (fired on warehouse receive)
never reached these bookings. Their handover moment is the load itself.
Extract notifyCarriageAcceptanceReady into a shared notifications util
(was private to WarehouseInventoryService) and call it from
BookingJourneyService.loadBooking for EXPORT + DIRECT_TO_TRAIN bookings,
right after the GRN gate, before the load transaction proceeds.
Intercity bookings ride the wagons freed by earlier unloads (e.g. import
containers uncoupled at Dire Dawa). loadBooking now auto-allocates a
DOMESTIC booking onto on-train slots whose cargo has all departed —
greedy in consist order by capacity, container numbers copied for the
marshalling tally. Falls back to unallocated load when nothing is free.