UI Adjustments, External Navigation Issues (#380)

* adjusted icon size on main about, adjusted text spacing

* design adjustments and spacings

* changed onboarding flow; user does not get navigated to screen 4 after declining tracing permission; explicit denial required

* catch exception when no browser or phone app installed

* fixed main overview a18n contrast issue

* merged external navigation helpers into single helper object

* adjusted bluetooth settings navigatioN

* added custom exception for external actions; added external action helper

* fixed build issues

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>