Only fuel types that currently have at least one favourite appear as
tabs; each tab ranks that fuel's favourites cheapest-first and the
narrative (crown header, section title, cheapest-favourite explainer)
names the active fuel.
- FuelType labels: 'Unleaded (E10)'/'Premium (E5)' -> 'Unleaded'/'Premium'
- New DistanceUnit (miles/km) preference; all app + widget distances,
radii and alert text convert/display in the chosen unit
- Settings tab (4th tab): segmented miles/km picker, 'Show introduction'
replay button (onboarding moved out of Alerts tab), StoreKit tip £4.99
- ProximityMonitor + widget notifications use the chosen unit
- Tests: label expectations updated, DistanceUnit conversion + format tests
FuelBoard Contributor