Starting trail recording with GPS switched off used to call setActive(true)
immediately -- the session timer ran while the screen sat on "Waiting for
GPS fix" forever and recorded nothing, with no hint that GPS was the
problem. Choosing "Start tracking" now opens a "GPS is off" confirmation
(Enable GPS & start / Cancel); confirming enables GPS and starts the
session. Behaviour is unchanged when GPS is already on.
Gated on a new UITask::hasGPS() so the prompt only appears on boards that
expose a toggleable GPS, not where GPS is simply absent.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>