[Onboarding Admin App] Edit and delete Domain Reviewers

The current implementation allows admins to create and delete new Domain Reviewers. The editing features are still missing, and the app doesn't ask for confirmation before permanently deleting a row.

Start by locating the Onboarding Admin App code that creates and deletes Domain Reviewers, then trace how reviewer rows are rendered and handled. The work is done when admins can edit existing Domain Reviewers and deleting a row requires confirmation before it is permanent.

Written by the indexing model from the issue text.