* fix(backend): validate the S3 endpoint host before the restore download
downloadFileFromS3() built an S3StorageAdapter and called .download()
directly, skipping the isHostAllowed() private-IP/DNS-rebinding guard
that testConnection() applies elsewhere — an admin with backup.restore
could point the configured S3 endpoint at an internal/metadata address
for unauthenticated egress via the server.
* fix(backend): pin the restore S3 download to its validated DNS resolution
isHostAllowed() was check-then-connect: the AWS SDK re-resolves the
endpoint hostname independently when it actually connects, so a DNS
rebinding condition between the preflight check and the real
connection could still reach a private/internal address. Reuses the
same pinnedRequestOptions() primitive webhookDeliveryWorker.js already
uses, wired into the S3Client's requestHandler.
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Co-authored-by: Paul Nothaft <paul@MacStudio-von-Paul.local>
Paul Nothaft