add wagon allocation snapshot to train schedules

apps/edr-freight-api/src/migrations/2120000000000-AddScheduleWagonAllocationSnapshot.ts

@@ -0,0 +1,34 @@
+import { MigrationInterface, QueryRunner } from "typeorm";
+
+/**
+ * Add a frozen wagon-allocation snapshot to each train schedule.
+ *
+ * Once a schedule leaves the editable DRAFT/SCHEDULED phase (dispatch / arrive /
+ * cancel), the same physical wagons get released and re-pinned onto later trains.
+ * The live wagon↔slot joins then no longer describe THIS train's plan, so an
+ * admin viewing a past schedule saw a mangled or "unavailable" allocation.
+ *
+ * This jsonb column stores a one-shot frozen copy of the wagon plan (per-slot
+ * physical wagon + booking allocations) captured at the transition. Non-editable
+ * schedules render from the snapshot; DRAFT/SCHEDULED still read live. NULL on
+ * legacy rows and while editable — the read path falls back to the live joins.
+ */
+export class AddScheduleWagonAllocationSnapshot2120000000000
+  implements MigrationInterface
+{
+  name = "AddScheduleWagonAllocationSnapshot2120000000000";
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      ALTER TABLE freight.train_schedules
+        ADD COLUMN IF NOT EXISTS wagon_allocation_snapshot jsonb;
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      ALTER TABLE freight.train_schedules
+        DROP COLUMN IF EXISTS wagon_allocation_snapshot;
+    `);
+  }
+}