KV backup restore

### What problem are you trying to solve?

I love Deno deploy and Deno KV. I can see myself using it as a primary database for many usecases. However, although I can set up backups to an S3 bucket, it doesn't look like I'd be able to restore a previous snapshot to the hosted KV database. To be specific, I'm not interested in hosting my own replica, but rather have the ability to go back to a previous point in time. For example, for whatever reason I want to restore my deno deploy hosted KV database to it's state two days ago.

### Describe the solution you'd like

It would be amazing if I was able to see and pick different snapshots to restore to from the deno deploy dashboard.

### Describe alternatives you've considered

None, really. I can live without it, but having this feature would give people a higher sense of security.

### Documentation, Adoption, Migration Strategy

_No response_

Start with the requested restore flow: choosing an earlier snapshot in the Deno Deploy dashboard and restoring the hosted KV database, rather than running a replica. The issue mentions S3 backups but names no implementation files or tests; ask maintainers where this work belongs and whether it is supported. Done means users can select a snapshot and restore hosted KV to that point in time.

Written by the indexing model from the issue text.