Add phpunit.xml and tests/Pest.php for standalone test execution. Apply Laravel Pint formatting fixes across all source files. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
P2-082: Webhook Signature Verification - Add require_signature field, verifySignatureWithDetails() - Support grace period during secret rotation - Log signature failures for audit P2-083: Webhook Delivery Logging - WebhookDeliveryLogger service for centralised logging - Track duration, response code, signature verification - Add getDeliveryStats() and getRecentSignatureFailures() Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>