isabelleandClaude Sonnet 5
451817f2e1
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>
