GHSA-fjwv-jf2v-j499

### Summary The SNS `UnsubscribeConfirmation` handler in `internal/integrations/ingestors/sns/sns.go` makes an unvalidated `http.Get()` call to `payload.UnsubscribeURL` without any URL restriction. Because `UnsubscribeURL` is intentionally excluded from the `BuildSignature()` signed field list, an attacker can replace this field in a legitimately AWS-signed message with an arbitrary internal URL, bypassing the `VerifyPayload()` signature check entirely and triggering a Server-Side Request Forgery (SSRF) against internal infrastructure — including the EC2 Instance Metadata Service (IMDS) at `169.254.169.254`. ### Impact This is a Server-Side Request Forgery (SSRF) vulnerability. An attacker with a Hatchet account and an AWS Free Tier account can: - Reach the EC2 IMDS endpoint and retrieve IAM temporary credentials if Hatchet is deployed on AWS - Port-scan and probe internal services not exposed to the internet - Access internal HTTP APIs (e.g., Kubernetes API server, internal dashboards) from the Hatchet server's network context