CHW-5405 PaddleWebhookStorage

paddle webhook event could not be persisted; paddle will retry the delivery

Default message: paddle webhook event could not be persisted; paddle will retry the delivery
HTTP status: 500 (server)

Problem. /api/paddle/webhook returned 500 without processing the event. Cause. The idempotency insert into paddle_webhook_events failed — DB down, disk full, or schema drift. Fix. No client action needed; Paddle retries non-2xx, so the next delivery will re-attempt the insert. Fix the DB and the replay will land cleanly. HTTP 500.