Get the public keys used to verify webhook signatures

Returns the set of Ed25519 public keys Ideogram uses to sign outbound webhook payloads. Customers verify incoming webhooks by recomputing the canonical signed message (request_id\nuser_id\ntimestamp\nsha256_hex(body)) and checking the X-Ideogram-Webhook-Signature header against any key in this document.

The document includes the current signing key plus any keys recently rotated out, so signatures already in flight remain verifiable across rotations. Cache for up to 24 hours; refresh sooner if a signature fails to verify against the cached set.

This endpoint is public and unauthenticated — no API key is required.