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-unit.util.ts

@@ -93,8 +93,12 @@ function unitsForShape(input: {
     case 'INTERCITY':
       return ['PER_CONTAINER', 'PER_TON', 'PER_WAGON', 'PER_KM'];
     case 'FIRST_MILE':
-    case 'LAST_MILE':
       return ['PER_CONTAINER', 'PER_TON', 'PER_KM', 'FLAT'];
+    case 'LAST_MILE':
+      // PER_KM = container mode (banded by distance + container size),
+      // PER_TON_KM = bulk mode (tons × km × rate). Legacy units kept for
+      // existing rows.
+      return ['PER_KM', 'PER_TON_KM', 'PER_CONTAINER', 'PER_TON', 'FLAT'];
     default:
       return ['FLAT'];
   }