Docker/OCI registry as additional Datalab storage option

[achtsnits]

See #75 for current state in regards to storage options and #76 for extension with relational db storage.

There is also a requirement to provide each team with access to its own dedicated Docker/OCI registry, manageable through command-line/API interface.

Goals

• Enable automatic provisioning of Docker/OCI registry when configured.
• Automatically inject credentials so that the registry can be directly accessed and used from within the Datalab environment (e.g., Terminal or VSCode Server).
• Expose credentials through Workspace UI.