Enable delete markers for buckets

[achtsnits]

In EOEPCA/workspace#74, we proposed enabling teams to distinguish between discoverable and non-discoverable buckets.

This distinction allows users to understand whether data has been shared (and is potentially used by others) or if it remains private and under their own control — helping teams determine what data is still relevant.

For non-discoverable buckets, teams could create short-lived buckets that can be marked for deletion once no longer needed.

Goal

• The Workspace UI should not trigger the immediate deletion of a bucket (including its stored data).
• Instead, it should allow marking a bucket for deletion, enabling an asynchronous cleanup job — configured by the operator — to handle data and bucket removal safely.