The widget/Live Activity showed straight-line haversine distance (0.8 mi)
while Apple Maps routes 1.8 mi. Road routing is too heavy for the widget
execution + ~40-70/day refresh budget, so the APP now computes it:
- New RoadDistanceService (app target): for the nearest 12 stations each
pass, calls MapKit MKDirections (free, no API key, matches Apple Maps)
and caches metres keyed by station ID.
- Cache stored in KEYCHAIN (fuelboard.roadDistances) so the widget reads it
even on free SideStore accounts with no app-group container; only valid
within 600 m of the location it was built from.
- Throttled: recompute max every 10 min, or when the user moves > 400 m;
wired into the location-update hook + location onChange.
- Widget face, app station rows + Live Activity show the cached road
distance, falling back to straight-line when absent.
- 4 new cache tests (105 total).
