Initial commit: ws_vatcheck at v1.0.3

Includes the fix for the GR/EL VAT prefix bug that broke exemption for
every Greek VAT number (in_array-on-values vs array_key_exists in
CacheTaxManager/VatNumber, plus the missing use import in
EuValidatorAdapter). Adds IMPROVEMENTS.txt with a checklist of features
adopted from comparing against the vatchecker module (offline-fallback
policy, failure logging, company-name check, configurable EU country
list, per-product exclusion, GB/XI mapping, AJAX live validation,
address-priority strategy).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

vendor/composer/autoload_classmap.php

@@ -0,0 +1,11 @@
+<?php
+
+// autoload_classmap.php @generated by Composer
+
+$vendorDir = dirname(__DIR__);
+$baseDir = dirname($vendorDir);
+
+return array(
+    'Composer\\InstalledVersions' => $vendorDir . '/composer/InstalledVersions.php',
+    'Ws_VatCheck' => $baseDir . '/ws_vatcheck.php',
+);