feat(warehouse): show the trucks in the yard, not just a count of them

Multi-truck self-haul had no list anywhere on the warehouse side. The ops
dashboard counted trucks on site and offered no way to open the list, and
the inventory table showed a blank plate on exactly the bookings that have
several trucks: it read booking.customer_truck_plate_number, which
multi-truck self-haul leaves null because plates live in
customer_truck_assignments. Booking BK-2026-000033 has a truck and a driver
on file and displayed neither.

Adds a Trucks on Site page listing every truck that has arrived and not yet
departed, across bookings, with plate, driver, booking, customer, containers
and dwell time. It covers both haulage paths because the gate does — a
customer's own truck and an EDR last-mile truck reach the same barrier — and
flags anything sitting over four hours. It lives under Warehouse Management
rather than Imports or Exports, since the yard is not per-direction.

The inventory queries now read plates and drivers from the assignments and
keep the booking columns as the fallback for single-truck bookings written
before that table existed.

Both new statements were EXPLAIN-validated against the live schema; the
plate fix returns the data that was previously null.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/edr-freight-web/backoffice/src/hooks/useWarehouses.ts

@@ -154,6 +154,15 @@ export function useWarehouseOpsStats() {
   });
 }
 
+/** Trucks in the yard right now — refreshes with the rest of the ops widgets. */
+export function useTrucksOnSite() {
+  return useQuery({
+    queryKey: ['warehouse-inventory', 'trucks-on-site'],
+    queryFn: () => warehouseService.trucksOnSite().then((r) => r.data),
+    refetchInterval: DASHBOARD_REFETCH_MS,
+  });
+}
+
 /** How often the live warehouse dashboard widgets auto-refresh (ms). */
 export const DASHBOARD_REFETCH_MS = 60_000;