export flow and fix intercity issue

apps/edr-freight-api/src/modules/contracts/contract-booking.service.ts

@@ -866,6 +866,7 @@ export class ContractBookingService {
     const completed = await this.bookingTransitionService.requestOperation(
       booking.id,
       dto.scheduledDate,
+      dto.trainScheduleId ?? null,
     );
     return { booking: completed, warnings };
   }

apps/edr-freight-api/src/modules/contracts/dto/create-booking-under-contract.dto.ts

@@ -175,6 +175,16 @@ export class CreateBookingUnderContractDto {
   @IsDateString()
   scheduledDate?: string;
 
+  @ApiPropertyOptional({
+    description:
+      'EXPORT rail only: the specific train (schedule id) picked from ' +
+      'GET /bookings/:id/export-trains for the shipment day. The reserve path ' +
+      'locks onto this train; 409 when it no longer fits. Ignored otherwise.',
+  })
+  @IsOptional()
+  @IsUUID()
+  trainScheduleId?: string;
+
   @ApiPropertyOptional({
     enum: SHIPMENT_EQUIPMENT_RETURNS,
     description: