Prevent and warn about applying a template that has unavailable model versions

Equivalent of #1204 (closed) but for model versions: backend#1429 (closed) will prevent applying a template that has unavailable model versions.

The template details view could include in its existing is-warning notification whether this template has unavailable model versions, or each version could have a ⚠ icon showing the problem. The template selection modal should disable its Apply button to prevent the user from applying such an invalid template.