implement empty-container return service: add return quantity handling, update related DTOs, services, and UI components

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

@@ -20,6 +20,7 @@ export const RATE_TYPES = [
   'OVERWEIGHT_PER_TON',
   'HAZARD_SURCHARGE',
   'REEFER_SURCHARGE',
+  'RETURN_SURCHARGE',
   'PIL_EXTRA_FEE',
   'CUSTOMS_CLEARANCE',
 ] as const;
@@ -71,6 +72,9 @@ export const RATE_TRIGGERS = [
   'HAZARDOUS',
   'OVERWEIGHT',
   'REEFER',
+  // Empty-container return service (container freight only) — fires when the
+  // booking ships WITH_RETURN, billed like hazard/reefer (usually PER_CONTAINER).
+  'WITH_RETURN',
   'SHIPPING_LINE',
   'CONSOLIDATION',
   'CANCELLATION',