enhance shipment form and booking process

apps/edr-freight-api/src/modules/train-scheduling/train-capacity.util.ts

@@ -86,6 +86,27 @@ function num(value: unknown, fallback = 0): number {
   return Number.isFinite(n) ? n : fallback;
 }
 
+/**
+ * Cargo tons of a booking: the stored VGM total when present, else the sum of
+ * its container lines (quantity × VGM per unit). The portal's container flow
+ * stores per-line VGM and leaves `cargoTotalWeightVgm` at 0 — reading the
+ * total alone made every such booking weigh only its tare.
+ */
+export function bookingCargoTons(booking: {
+  cargoTotalWeightVgm?: number | string | null;
+  bookingContainers?: Array<{
+    quantity?: number | null;
+    vgmPerUnitTons?: number | string | null;
+  }> | null;
+}): number {
+  const total = num(booking.cargoTotalWeightVgm);
+  if (total > 0) return total;
+  return (booking.bookingContainers ?? []).reduce(
+    (sum, line) => sum + num(line.quantity) * num(line.vgmPerUnitTons),
+    0,
+  );
+}
+
 /** Gross weight of one loaded wagon: it hauls itself plus its cargo. */
 export function grossWagonWeightTons(slot: Pick<ConsistSlot, 'tareWeightTons' | 'cargoTons'>): number {
   return num(slot.tareWeightTons) + num(slot.cargoTons);
@@ -260,11 +281,34 @@ export function minLocomotiveLimits(
   };
 }
 
-function minConfigured(values: Array<number | string | null | undefined>): number {
+function minConfigured(values: Array<number | null | undefined>): number {
   const configured = values.filter((v) => v != null).map((v) => num(v));
   return configured.length ? Math.min(...configured) : 0;
 }
 
+/**
+ * Effective limits for a whole train set: min across its linked locomotives,
+ * falling back to the legacy single `locomotive` column for sets created
+ * before multi-loco support. Null when the set has no locomotive at all.
+ */
+export function trainSetLocomotiveLimits(
+  trainSet?: {
+    locomotive?: LocomotiveLimits | null;
+    locomotives?: Array<{ locomotive?: LocomotiveLimits | null }> | null;
+  } | null,
+): LocomotiveLimits | null {
+  if (!trainSet) return null;
+  const linked = (trainSet.locomotives ?? [])
+    .map((link) => link.locomotive)
+    .filter((l): l is LocomotiveLimits => Boolean(l));
+  const pool = linked.length
+    ? linked
+    : trainSet.locomotive
+      ? [trainSet.locomotive]
+      : [];
+  return minLocomotiveLimits(pool);
+}
+
 /** Per-booking train length from wagon count and freight-specific wagon type length. */
 export function bookingTrainLengthMeters(
   freightType: string | null | undefined,