add yard distances management to rule engine

- Introduced new yard distances resource with CRUD operations.
- Created migration for yard distances table with necessary constraints.
- Implemented service and repository for yard distances handling.
- Added controller for API endpoints to manage yard distances.
- Updated rule engine configuration to include yard distances.
- Enhanced rule engine resource page to support yard distance selection.
- Updated contracts and train builder pages to handle new yard distance logic.
- Added error handling utility for better error message extraction.

apps/edr-freight-api/src/modules/trains/train-builder.service.ts

@@ -29,6 +29,9 @@ import {
 
 const round = (value: unknown) => Math.round((Number(value) || 0) * 100) / 100;
 
+/** Locomotive statuses that block a train from reactivating. */
+const UNFIT_FOR_REACTIVATION = new Set(['MAINTENANCE', 'OUT_OF_SERVICE', 'UNAVAILABLE']);
+
 /** The one active (DRAFT/SCHEDULED/DISPATCHED) schedule surfaced per built train. */
 export interface ActiveScheduleRef {
   id: string;
@@ -596,11 +599,30 @@ export class TrainBuilderService {
     return this.getComposition(id);
   }
 
-  /** Reactivate a DEACTIVATED train back to AVAILABLE so it can be scheduled again. */
+  /**
+   * Reactivate a DEACTIVATED train back to AVAILABLE so it can be scheduled
+   * again. Blocked if any coupled locomotive is unfit for service — a
+   * deactivated train can sit parked for a while and its locomotives may have
+   * since been sent to maintenance independently; reactivating must not wave
+   * a down locomotive back onto the schedule board.
+   */
   async activate(id: string) {
     const train = await this.dataSource.getRepository(Train).findOne({ where: { id } });
     if (!train) throw new NotFoundException(`Train ${id} not found`);
     if (train.status === Freight.TrainStatus.Deactivated) {
+      const links = await this.dataSource
+        .getRepository(TrainLocomotive)
+        .find({ where: { trainId: id }, relations: { locomotive: true } });
+      const unfit = links
+        .map((link) => link.locomotive)
+        .filter((loco): loco is Locomotive => Boolean(loco))
+        .filter((loco) => UNFIT_FOR_REACTIVATION.has(loco.status));
+      if (unfit.length) {
+        const names = unfit.map((l) => `${l.code} (${l.status})`).join(', ');
+        throw new ConflictException(
+          `Train cannot be reactivated: ${names} ${unfit.length > 1 ? 'are' : 'is'} not fit for service. Detach and replace before reactivating.`,
+        );
+      }
       await this.dataSource
         .getRepository(Train)
         .update(id, { status: Freight.TrainStatus.Available });