How do we handle clearing all records when on a public computer

This is a follow up for [discussion 43](https://github.com/orgs/CulverLab/discussions/43)

When a user is on a public computer all records should be cleared when they log out. To support this a question regarding a trusted device should be part of the login screen - defaulting to a trusted computer.

What remains to be determined is what to do if the user doesn't logout on a public computer.

Perhaps catch the following events and clear the records when (some may not be possible):
- browser closing
- tab closing
- user logout of computer without closing browser

Further discussions in the comments

Start with discussion 43 and the follow-up questions in this issue. Define the intended trusted-device behavior and which browser or computer events can reliably trigger record clearing. Done means the public-computer logout and non-logout cases have an agreed, implementable specification.

Written by the indexing model from the issue text.