Fixes a webhook race: a late order:cancelled event could flip a paid WC order (status=processing) back to cancelled. Now all WC paid statuses (processing, completed, refunded, cancelled, plus custom shop statuses from wc_get_is_paid_statuses()) are protected. Caught by Docker-based E2E test suite introduced in this release. Also adds shoppex_pay_api_base filter for local dev / E2E against a non-production backend.