Feature: Add Box Now locker delivery integration

Box Now rate driver (fixed pricing only — no live pricing API) and fulfillment service (delivery request creation, label printing, cancellation). Unlike ACS, Box Now books courier pickup automatically on delivery request creation, so no manifest/pickup-list step is implemented. Storefront locker selection is not yet built; createShipment() expects the chosen locker's locationId to be supplied by the caller.

src/Shipping/Carriers/BoxNow/Exceptions/BoxNowApiException.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Modules\Core\Shipping\Carriers\BoxNow\Exceptions;
+
+use RuntimeException;
+
+class BoxNowApiException extends RuntimeException
+{
+    public function __construct(string $message, public readonly array $body = [])
+    {
+        parent::__construct($message);
+    }
+}