Allow admin users to view and manage sharing for all prototypes

### What feature do you want to see added?

Allow admin users to view and manage sharing for all prototypes.

### Why do you want this feature? Does it solve a problem?

This would allow admin users to have oversight of all prototypes in the platform.

### How should the feature be implemented?

It should reuse the existing layouts and views as much as possible, but be clear to the user that they're viewing someone else's prototype.

A separate screen should be used for viewing all prototypes, as opposed to just viewing the ones they can access.

If they edit it, it should be saved to their private workspace.

### Additional context (if applicable)

This follows on from #128.

No files, tests, or entry points are named. Start by locating the existing prototype access, sharing, layout, and workspace flows, then trace how an admin's separate all-prototypes screen can reuse them. Done means admins can view and manage sharing for every prototype, see clearly when a prototype belongs to someone else, and have edits saved to their private workspace.

Written by the indexing model from the issue text.