Setting the default currency through the UI doesn't work because of a `MouseArea` that
is masking the an underlying `StatusRadioButton` which will tricker the default currency
change.
This commit enhances the `MouseArea` to trigger the default currency change and it
also ensures the UI is responding accordingly. Namely that the new default currency
is correcly selected in the list of currencies.
There's also a little change in the background hover color so it works well across
light and dark themes.
Fixes#1632
c328f332f6