applet: implement UI tracking for the Context state

in particular WRT connection problems.

while the context is attempt to autoconnect we'll tell the user to hold on

if the context autoconnects discontinue we further offer a button for the user to manually reconnect to the daemon (e.g. after having fixed whatever was wrong with it)

testing

to break the connection

systemctl --user --runtime mask --now pipewire.service

to fix it again

systemctl --user --runtime unmask --now pipewire.service
systemctl --user start pipewire.service