Some suggestions for the UI

### Your use case

#### What would you like to do?
Improve the UI

#### Why would you like to do it?
I kinda like the current UI, but it would be nice to
- make the green-unread-message-indicator thing round in the rooms list
- remove the borders
- add a background to the composer's “Message…” column
- make the text title background the same as the app background in the room settings screen (and the “Homeserver” screen as well)

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

### Have you considered any alternatives?

_No response_

### Additional context

Those are the things that bothers me :)