feat(billing): add PNR row to freight invoice from booking payment reference

PNR isn't a column on Invoice/Payment — it's written onto Booking.pnrCode
when a CBE_BILL payment initiates. toDocumentModel() now looks it up by
invoice.sourceId and adds it to the existing summary grid, shown only
when present.

apps/edr-freight-api/src/modules/billing/billing.service.ts

@@ -513,6 +513,17 @@ export class BillingService {
     // MoR EIMS reference — only once actually registered, never a placeholder row.
     if (invoice.eimsIrn) summary.push({ label: "EIMS IRN", value: invoice.eimsIrn });
 
+    // PNR — the CBE_BILL reference the customer pays against, written onto the booking at
+    // payment-initiation time (see initiatePayment()). Not a column on Invoice/Payment, so
+    // look it up by source id; only shown once a payment actually generated one.
+    if (invoice.source === Freight.InvoiceSource.Booking) {
+      const booking = await this.dataSource.getRepository(Booking).findOne({
+        where: { id: invoice.sourceId },
+        select: ["id", "pnrCode"],
+      });
+      if (booking?.pnrCode) summary.push({ label: "PNR", value: booking.pnrCode });
+    }
+
     return {
       kind,
       title,