feat(bookings): add estimated shipment date handling and validation for binding shipment day

apps/edr-freight-api/src/modules/bookings/entities/booking.entity.ts

@@ -155,10 +155,23 @@ export class Booking extends BaseEntity {
   /**
    * Nullable: general contracts have no shipment date at creation — the date is
    * chosen per drawdown order. One-time bookings always set this (the pool day key).
+   *
+   * NOTE: this is the BINDING shipment day, validated against actual open train
+   * departures. It is set later, when the customer requests the operation — NOT
+   * at booking creation. See estimatedShipmentDate for the non-binding estimate
+   * captured in the booking wizard.
    */
   @Column({ name: 'scheduled_date', type: 'timestamptz', nullable: true })
   scheduledDate?: Date | null;
 
+  /**
+   * Non-binding shipment-date estimate captured in the booking wizard. Purely
+   * informational — NOT validated against train departures. The binding
+   * scheduledDate is chosen later at the operation-request step.
+   */
+  @Column({ name: 'estimated_shipment_date', type: 'timestamptz', nullable: true })
+  estimatedShipmentDate?: Date | null;
+
   /**
    * General contracts only: when the ordering window closes, computed from the
    * global CONTRACT_PERIOD_MONTHS setting at activation. Null for one-time