When the operator scans a license plate on the POS landing page, the
frontend now needs to display 'last washed' so they can decide whether a
DHL trailer needs another wash before pick-up (DRIFT 17).
- orders_o::getLastWashTimestampForPlate(reg_1) returns the created_at
of the most recent non-deleted order that has at least one non-deleted
order item, matching the contract used by
customer_vehicles_o::getLastOrderByPlate().
- GET /numberplatescans now enriches each scan with a 'last_wash' key
(MySQL DATETIME or null).
- New Pest test: tests/Unit/Orders/OrderLastWashTimestampForPlateTest.php
asserts both the helper and the route wiring.