Add double confirmation selection modal

Raised in #123, there are a few places in our UI we might want a double confirmation pattern in the modal. This would probably be project deletion, but perhaps also user account removal -- anything that is destructive, critical, and irreversible might be a good candidate.

I raised issue with text double confirmation, but I'd love to use a multiple choice selection double confirmation in a modal if we can. It wouldn't be much harder, but we could always start with either.

For a text input UI I'd probably just use the "Type delete" version, as the other forms of "Type the name of your project" are tedious and we only need to interrupt the user. I'd go this way if we're only adding this in two places.

A selection UI could show a few options, and the selected option has to match the instance that triggered the modal in the first place. This provides us with better confirmation and is less work from the user than typing. I'd go this way if/once we want to bring this to admin UI list tables/etc. We don't have bulk delete operations in our UI, so this would at least be less tedious than typing.

Screencast from 2023-03-30 19-35-50.webm

Start by reviewing issue #123 and the linked screencast to understand the proposed double-confirmation interaction. Clarify whether the project wants text confirmation or multiple-choice selection, and which destructive actions are in scope; done requires an agreed modal pattern applied to those specified actions.