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>

src/Adapter/EuValidatorAdapter.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace Websmid\VatCheck\Adapter;
+
+use PH7\Eu\Vat\Validator;
+use PH7\Eu\Vat\Provider\Europa;
+use PH7\Eu\Vat\Exception;
+use Websmid\VatCheck\Config\Config;
+use Websmid\VatCheck\Model\VatCache;
+
+class EuValidatorAdapter
+{   
+    protected $vatNr = '';
+
+    protected $isoCode = '';
+
+    private $checkStatus;
+
+    public function __construct(string $vatNr, string $isoCode)
+    {
+        $this->vatNr = str_replace($isoCode, '', $vatNr);
+        $this->isoCode = $isoCode;
+    }
+
+    public function checkAndStore()
+    {
+        try {
+            $euVatValidator = new Validator(new Europa, $this->vatNr, $this->isoCode);
+        } catch(Exception $e){
+            return false;
+        }
+
+        if( $euVatValidator instanceof Validator ){
+            $fullVat = $this->isoCode.$this->vatNr;
+            $vatCache = VatCache::getOrCreateByVat($fullVat);
+            $vatCache->vat_nr = $fullVat;
+            $vatCache->valid = $euVatValidator->check();
+
+            $vatCache->save();
+        }
+
+        return true;
+    }
+}