feat(warehouses): track physical container stack and slot positions

Extends the warehouse hierarchy below zone with ground stacks and vertical
slots, so a container's exact position is recorded rather than only its zone.

- freight.warehouse_zone_stacks / warehouse_zone_slots, plus nullable
  stack_id / slot_id on warehouse_inventory (existing rows stay valid)
- slot occupancy is derived from inventory status, guarded by a partial
  unique index, so no exit path has to remember to free a slot
- placement service: hierarchy validation, bottom-up stacking rules,
  accessibility/blocking-container reads, capacity vs slot summaries
- stack CRUD with auto-generated slots; reuses warehouse-zone permissions
- slot support folded into the existing move()/store() paths
- fix: validateLocation now rejects a mismatched warehouse/yard/zone triple
- seed:warehouse-layout builds the layout from a JSON config

apps/edr-freight-api/src/scripts/seed-warehouse-layout.ts

@@ -0,0 +1,35 @@
+import { AppDataSource } from '../data-source';
+import { WarehouseLayoutSeeder } from '../seed/warehouse-layout.seeder';
+
+/**
+ * Lays out the physical warehouse structure described by
+ * `src/seed/warehouse-layout.json` — edit that file, not this script.
+ *
+ * Idempotent: existing warehouses, yards, zones, stacks and slots are left
+ * untouched, so a re-run only fills in what is missing.
+ */
+async function seedWarehouseLayout() {
+  await AppDataSource.initialize();
+
+  try {
+    const summary = await new WarehouseLayoutSeeder(AppDataSource).run();
+    console.table([summary]);
+
+    const counts = await AppDataSource.query(`
+      SELECT
+        (SELECT COUNT(*)::int FROM freight.warehouses WHERE deleted_at IS NULL) AS warehouses,
+        (SELECT COUNT(*)::int FROM freight.warehouse_yards WHERE deleted_at IS NULL) AS yards,
+        (SELECT COUNT(*)::int FROM freight.warehouse_zones WHERE deleted_at IS NULL) AS zones,
+        (SELECT COUNT(*)::int FROM freight.warehouse_zone_stacks WHERE deleted_at IS NULL) AS stacks,
+        (SELECT COUNT(*)::int FROM freight.warehouse_zone_slots WHERE deleted_at IS NULL) AS slots
+    `);
+    console.table(counts);
+  } finally {
+    await AppDataSource.destroy();
+  }
+}
+
+seedWarehouseLayout().catch((error) => {
+  console.error('Failed to seed the warehouse layout:', error);
+  process.exit(1);
+});