Decide whether & how to show encryption status

### Your use case

#### What would you like to do?

When a user's key is not available for some reason, indicate that in some way in the UI, maybe? We don't have to have a special tile design for this, but some way to progressively disclose the kind of encryption failure to a motivated technical user would be welcome.

#### Why would you like to do it?

If Element Call is not working, I want to be able to uncover some indication of *why* it's not working.

#### How would you like to achieve it?

Bring back Hugh's encryption status code & maybe iterate the UI

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

Start by investigating the previously mentioned encryption status code from Hugh and the current Element Call UI behavior when a user's key is unavailable. Define how encryption failures should be progressively disclosed to technical users, then validate the proposed indication across the failure scenarios described in the issue.

Written by the indexing model from the issue text.