Webhooks: get told when work finishes, instead of polling

POST /v1/decks returns in milliseconds and the deck takes minutes, so until now the only way to find out it was ready was to keep asking. You can now register an endpoint under Settings → Developers and we will POST to it the moment a deck finishes or fails, an SEO audit completes, or an AEO scan finishes.

Every delivery is signed, so you can verify it came from us: the secret is shown once when you add the endpoint, and rotating it is one click. The endpoint list shows the last delivery and, more usefully, the failures — an endpoint that has been quietly rejecting us for days looks exactly like a quiet week otherwise.