Resolves TRU-78 (DRIFT 17: License plate scan - show 'last washed'
timestamp on landing page / DHL use case).
The POS landing page already surfaces license plate scans via `GET
/numberplatescans`, but it has no way to tell the operator **when a
plate was last washed**. With DHL trailers going in and out several
times a day, the front-desk needs that hint to decide whether a trailer
needs another wash before pick-up.
## Changes
- **`orders_o::getLastWashTimestampForPlate(string $reg_1): ?string`** —
new helper that returns the `created_at` (MySQL DATETIME) of the most
recent non-deleted order for the plate that has at least one non-deleted
order item. Mirrors the contract used by
`customer_vehicles_o::getLastOrderByPlate()` so the timestamp is always
backed by a real wash.
- **`GET /numberplatescans`** now enriches each scan row with a
`last_wash` key (string or `null`). No breaking change to the existing
payload; new field is additive.
- **New Pest test**
`services/nginx/app/tests/Unit/Orders/OrderLastWashTimestampForPlateTest.php`
— static-analysis assertions for the helper definition and the route
wiring (matches the style of `OrderBookingsCountsRouteWiringTest`).
## Frontend companion
https://github.com/copenhagentruckwash/pleno-vue/pull/335 renders this
`last_wash` in the inline details of each scan row on the POS landing
page (`PosLastScannedLicensePlatesV2.vue`), with an "Aldrig vasket" /
"Never washed" fallback when the API returns `null`.
## Risk
- `getLastWashTimestampForPlate` does one extra indexed read per scan
row (`SELECT id FROM orders WHERE reg_1 = ? AND deleted_at IS NULL`).
The existing `isPlateSeenBefore` call already does the same, so the
route's per-row query count is unchanged in shape.
- The new field is additive and ignored by older clients, so this can
roll forward without a coordinated client release.
Co-authored-by: openclaw bugfix <openclaw@copenhagentruckwash.local>
