1.0.0

Added

• Initial public release: getting-started, API client, offers, order-and-cart, order-lifecycle,
  paywall-token, webhooks, request-signing, multi-tenant, and troubleshooting docs.
• Runnable Docker demo (PHP 8.1-fpm-alpine + nginx) covering the core payment flow: offers, order
  create/status/cancel, paywall auth token, and a webhook receiver.
• Copy-paste snippets: api-client.php, create-order.php, paywall-token.php, verify-webhook.php.
• Multi-tenant support with per-shop credential resolution (config/shops.php), demoed via two
  sample tenants (shop-a, shop-b).