feat(train-scheduling): show loaded empties on the marshalling document

Empty containers loaded onto an export departure carry no booking and no
wagon allocation, so their wagons printed as EMPTY — no cargo allocated —
staff checking the paper against the consist found boxes the list denied.
Those wagons now print the container numbers with cargo type EMPTY
CONTAINER, count toward the 40ft/20ft tallies, and get their own summary
tile; only genuinely bare wagons keep the empty wording.

apps/edr-freight-api/src/modules/train-scheduling/services/train-scheduling.service.spec.ts

@@ -1132,6 +1132,36 @@ describe('TrainSchedulingService', () => {
       expect(html).toContain('2 (1 empty)');
     });
 
+    it('lists loaded empty containers by number and states they are empty', () => {
+      const schedule = {
+        id: 'schedule-1',
+        trainNumber: '8301',
+        direction: 'EXPORT',
+        trainSet: {
+          wagons: [makeWagon(1, 'W-001', []), makeWagon(2, 'W-002', []), makeWagon(3, 'W-003', [])],
+        },
+        scheduleBookings: [],
+      };
+
+      const html = (service as never as {
+        buildExportLoadListHtml: (s: unknown, o?: unknown) => string;
+      }).buildExportLoadListHtml(schedule, {
+        emptyContainers: [
+          { containerNumber: 'CMU9876543', containerSize: '40', wagonSequenceNo: 1 },
+          { containerNumber: 'TEMU1112223', containerSize: '20', wagonSequenceNo: 2 },
+          { containerNumber: 'TEMU4445556', containerSize: '20', wagonSequenceNo: 2 },
+        ],
+      });
+
+      expect(html).toContain('CMU9876543');
+      expect(html).toContain('TEMU1112223, TEMU4445556');
+      expect(html.match(/EMPTY CONTAINER/g)).toHaveLength(2);
+      // Wagon 3 carries nothing at all, so it keeps the bare-wagon wording.
+      expect(html.match(/EMPTY — no cargo allocated/g)).toHaveLength(1);
+      expect(html).toContain('3 (1 empty)');
+      expect(html).toContain('<span>Empty containers</span><strong>3</strong>');
+    });
+
     it('renders wagons in consist order regardless of the order the relation returns', () => {
       const schedule = {
         id: 'schedule-1',