Visual indication of bluetooth connectivity and auto-illuminate

[lemeryfertitta]

It would be convenient to be able to automatically illuminate climbs after switching on the app. We could use the lighbulb to toggle "connected/disconnected" without actually disconnecting. We would want a visual indication of this, and we can use the filled lightbulb icon to do so (and maybe switch the button to be filled blue instead of outline).

Split from #45