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/migrations/2060000000000-CreateYardDistances.ts

@@ -0,0 +1,66 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+/**
+ * Configured rail distance between two yards (Configuration → Yard Distances).
+ * Route creation resolves each segment's km from here (symmetric lookup:
+ * one A↔B row serves both directions) instead of accepting free-text km,
+ * and snapshots the value onto route_milestones.distance_km.
+ *
+ * Uniqueness is a partial index (deleted_at IS NULL) so a soft-deleted pair
+ * can be re-created.
+ */
+export class CreateYardDistances2060000000000 implements MigrationInterface {
+  name = 'CreateYardDistances2060000000000';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      CREATE TABLE IF NOT EXISTS freight.yard_distances (
+        id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+        from_yard_id uuid NOT NULL REFERENCES freight.yards(id),
+        to_yard_id uuid NOT NULL REFERENCES freight.yards(id),
+        distance_km numeric(10,2) NOT NULL,
+        created_at timestamptz NOT NULL DEFAULT now(),
+        updated_at timestamptz NOT NULL DEFAULT now(),
+        deleted_at timestamptz
+      );
+    `);
+    await queryRunner.query(`
+      CREATE INDEX IF NOT EXISTS idx_yard_distances_from_yard
+        ON freight.yard_distances (from_yard_id);
+    `);
+    await queryRunner.query(`
+      CREATE INDEX IF NOT EXISTS idx_yard_distances_to_yard
+        ON freight.yard_distances (to_yard_id);
+    `);
+    await queryRunner.query(`
+      CREATE UNIQUE INDEX IF NOT EXISTS uq_yard_distances_pair
+        ON freight.yard_distances (from_yard_id, to_yard_id)
+        WHERE deleted_at IS NULL;
+    `);
+    // Backfill from segments already stored on existing routes so editing them
+    // does not immediately fail the "pair not configured" check. One row per
+    // unordered pair; where routes disagree the longest segment wins.
+    await queryRunner.query(`
+      INSERT INTO freight.yard_distances (from_yard_id, to_yard_id, distance_km)
+      SELECT DISTINCT ON (LEAST(prev_yard_id, yard_id), GREATEST(prev_yard_id, yard_id))
+        prev_yard_id, yard_id, distance_km
+      FROM (
+        SELECT
+          yard_id,
+          distance_km,
+          LAG(yard_id) OVER (PARTITION BY route_id ORDER BY sequence_no) AS prev_yard_id
+        FROM freight.route_milestones
+        WHERE deleted_at IS NULL
+      ) segments
+      WHERE prev_yard_id IS NOT NULL
+        AND distance_km IS NOT NULL
+        AND distance_km > 0
+      ORDER BY LEAST(prev_yard_id, yard_id), GREATEST(prev_yard_id, yard_id), distance_km DESC
+      ON CONFLICT DO NOTHING;
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`DROP TABLE IF EXISTS freight.yard_distances;`);
+  }
+}