Files tab issues

Issue 1

When you are not loggedin or you are not a participant of the competition, you see this in the files tab which is misleading

Instead, we should show registration+login when not loggedin and register when not a participant

Issue 2:

Whe you are a participant, you see available column, which I think should be shown to organizers only

Todos:

• show login/signup message in files tab if not signed in
• hide available column if not organizaer