feat(rule-engine): add fuel surcharge rate trigger and cargo flag

apps/edr-freight-api/src/contracts/contract-rate-schedule.builder.ts

@@ -44,6 +44,7 @@ const UNIT_LABELS: Record<string, string> = {
   PER_CONTAINER: 'per container',
   PER_KM: 'per km',
   PER_TON_KM: 'per ton per km',
+  PER_LITER: 'per liter',
   PER_INVOICE: 'per invoice',
   FLAT: 'flat',
 };
@@ -66,6 +67,7 @@ const TRIGGER_ROUTE_LABELS: Partial<Record<Rate['trigger'], string>> = {
   DEMURRAGE: 'Demurrage / wagon detention',
   PIL_EXTRA_FEE: 'PIL shipping line extra fee',
   CUSTOMS_CLEARANCE: 'Customs clearance service',
+  FUEL: 'Fuel surcharge',
 };
 
 @Injectable()
@@ -101,6 +103,15 @@ export class ContractRateScheduleBuilder {
         continue;
       }
 
+      // Fuel is sold per lane + commodity — only lanes matching the contract's
+      // direction belong on its schedule, labeled with their leg.
+      if (rate.trigger === 'FUEL') {
+        if (this.fuelDirectionMatches(rate, direction)) {
+          surcharges.push(this.fuelRow(rate));
+        }
+        continue;
+      }
+
       // Everything left is a trigger-based charge (surcharge / demurrage / customs).
       surcharges.push(this.surchargeRow(rate));
     }
@@ -176,6 +187,26 @@ export class ContractRateScheduleBuilder {
     };
   }
 
+  private fuelDirectionMatches(rate: Rate, direction: ContractDirection): boolean {
+    const want =
+      direction === 'IMP' ? 'IMPORT' : direction === 'EXP' ? 'EXPORT' : 'DOMESTIC';
+    return rate.tradeDirection === want;
+  }
+
+  /** Fuel row — the lane matters, so it rides along in the charge label. */
+  private fuelRow(rate: Rate): RateScheduleRow {
+    const origin = rate.originYard?.label ?? rate.originYard?.code ?? '—';
+    const destination =
+      rate.destinationYard?.label ?? rate.destinationYard?.code ?? '—';
+    return {
+      route: `Fuel surcharge (${origin} → ${destination})`,
+      cargo: this.cargoLabel(rate),
+      currency: rate.currency,
+      amount: this.formatAmount(rate.rateValue),
+      unit: this.unitLabel(rate.rateUnit),
+    };
+  }
+
   private surchargeRow(rate: Rate): RateScheduleRow {
     return {
       route: TRIGGER_ROUTE_LABELS[rate.trigger] ?? this.titleCase(rate.trigger),