Feature: Add ACS courier integration

ACS rate driver (live price quotes via ACS_Price_Calculation, cached postcode-to-station lookups) and fulfillment service (voucher creation, label printing, end-of-day pickup manifest). Adds a per-rate pricing_mode column so admins can choose live API pricing vs. a fixed price on ACS-driven shipping rates, surfaced via a custom Rates page.

src/Shipping/Carriers/Acs/Exceptions/AcsApiException.php

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