feat(rates): last-mile rate rules with bulk per-ton-km and container distance bands

- rates: min_km/max_km columns, PER_TON_KM unit, ETB|USD currency for last mile
- extend UQ_rates_pattern with band start; overlap + shape validation
- shared last-mile charge resolver; approve-dialog price estimate endpoint
- delivery-fee invoice prices via rules, falls back to vehicle price/km
- backoffice: last-mile rate form (mode, container type, band, currency)

apps/edr-freight-api/src/modules/rule-engine/entities/rate.entity.ts

@@ -39,6 +39,8 @@ export const RATE_UNITS = [
   'PER_ITEM',
   'PER_CONTAINER',
   'PER_KM',
+  // Last-mile bulk: price = tons × km × rateValue.
+  'PER_TON_KM',
   'PER_INVOICE',
   'FLAT',
 ] as const;
@@ -156,6 +158,17 @@ export class Rate extends BaseEntity {
   @Column({ name: 'rate_unit', type: 'varchar', length: 30 })
   rateUnit!: RateUnit;
 
+  /**
+   * Distance band for container last-mile rates (rateUnit = PER_KM, scoped by
+   * containerTypeId): the rate applies when minKm <= km < maxKm (maxKm NULL =
+   * open-ended). NULL on every other rate shape.
+   */
+  @Column({ name: 'min_km', type: 'numeric', precision: 10, scale: 2, nullable: true })
+  minKm?: number | null;
+
+  @Column({ name: 'max_km', type: 'numeric', precision: 10, scale: 2, nullable: true })
+  maxKm?: number | null;
+
   @Column({ name: 'status', type: 'varchar', length: 20, default: 'DRAFT' })
   status!: RateStatus;