[Docs] Backup & Restore Documentation

While not explicitly mentioned as part of the PRR Process for Experiment stage, because we are a source-of-state, we should attempt to satisfy backup/restore procedure documentation requirements ahead of their introduction in Beta stage.

We internally merge two sources of data:

1. CloudSQL, which has backup information here: https://docs.runway.gitlab.com/runtimes/cloud-run/managed-services/cloudsql/#backups-always-on
2. GCP KMS, which to my knowledge has no informed backup procedure other than what is internally documented. If Google loses this keys, we lose relevant data. Long term, this will be handled by https://github.com/openbao/openbao/issues/1021 upstream.

We should synthesize this into the production readiness document and perhaps complete the Beta stage requirements early, along with testing PostgreSQL level snapshotting/restore to check for broken state.