Enhance wagon capacity handling and validation in booking service

- Added default capacities for container and bulk wagons.
- Updated wagonsFor method to consider weight and length for wagon calculations.
- Improved handling of overweight bookings with appropriate warnings.
- Adjusted tests to reflect changes in wagon capacity and validation logic.

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

@@ -731,3 +731,76 @@ describe('BookingBatchService — PAID reconcile', () => {
     });
   });
 });
+
+describe('BookingBatchService — wagonsFor', () => {
+  // wagonsFor is pure arithmetic over its two arguments and touches no injected
+  // dependency, so the service can be built with none.
+  const service = new BookingBatchService(
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+    null as never,
+  ) as unknown as {
+    wagonsFor(booking: unknown, dims: unknown): number;
+  };
+
+  // PW2 box wagon: 70T rated payload, 25.2T tare, 17.066m.
+  const dims = {
+    container: { lengthMeters: 13.966, tareWeightTons: 22.4, capacityTons: 70 },
+    bulk: { lengthMeters: 17.066, tareWeightTons: 25.2, capacityTons: 70 },
+  };
+
+  const bulk = (cargoTons: number, over: Record<string, unknown> = {}) => ({
+    freightType: 'BULK',
+    cargoTotalWeightVgm: cargoTons,
+    bookingContainers: [],
+    ...over,
+  });
+
+  it('sizes a bulk booking by cargo ÷ rated payload, not a flat 1 wagon', () => {
+    // 37 × 1400 fertilizer packages × 50kg = 2590T of cargo.
+    expect(service.wagonsFor(bulk(2590), dims)).toBe(37);
+  });
+
+  it('rounds a partial wagon up', () => {
+    expect(service.wagonsFor(bulk(70.1), dims)).toBe(2);
+    expect(service.wagonsFor(bulk(70), dims)).toBe(1);
+  });
+
+  it('still floors at one wagon when a bulk booking has no recorded cargo', () => {
+    expect(service.wagonsFor(bulk(0), dims)).toBe(1);
+  });
+
+  it('honours an explicit wagonsRequired override', () => {
+    expect(service.wagonsFor(bulk(2590, { wagonsRequired: 40 }), dims)).toBe(40);
+  });
+
+  it('takes the binding axis for containers: weight can exceed TEU geometry', () => {
+    // Two 40ft units => 2 wagons by TEU geometry, but 210T needs 3 at 70T each.
+    const booking = {
+      freightType: 'CONTAINER',
+      cargoTotalWeightVgm: 210,
+      bookingContainers: [
+        { quantity: 2, wagonsRequired: 2, containerType: { wagonsPerUnit: 1, sizeFt: 40 } },
+      ],
+    };
+    expect(service.wagonsFor(booking, dims)).toBe(3);
+  });
+
+  it('keeps TEU geometry when it binds before weight', () => {
+    // Four 20ft units => 2 wagons by geometry; 40T of cargo needs only 1 by weight.
+    const booking = {
+      freightType: 'CONTAINER',
+      cargoTotalWeightVgm: 40,
+      bookingContainers: [
+        { quantity: 4, wagonsRequired: 2, containerType: { wagonsPerUnit: 0.5, sizeFt: 20 } },
+      ],
+    };
+    expect(service.wagonsFor(booking, dims)).toBe(2);
+  });
+});