Warn when the user's audio input is completely silent

### Your use case

#### What would you like to do?

If you've unmuted yourself in a call or in the lobby, but your audio input is completely silent, the app should warn you about it.

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

Because audio issues are annoying to troubleshoot, and if the app can communicate that it's an issue with your audio setup rather than the app itself, that makes it a lot easier to solve (and makes users less likely to start distrusting the app).

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

We could do what Jitsi does, where they have a "Your microphone is working" checkmark on the lobby screen, or we could have warnings that pop up in response to being unmuted during a call.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_