Drop deprecated MapKit and ActivityKit calls, and a dead capture

- RoadDistanceService builds route endpoints with MKMapItem(location:address:)
  instead of the MKPlacemark path deprecated in iOS 26.
- LiveActivityManager updates through ActivityContent, replacing the
  ActivityKit update(using:) call deprecated in iOS 16.2.
- The location-update hook no longer captures an unused state object; the
  closure body already runs on self, so behaviour is unchanged.

FuelBoard/ContentView.swift

@@ -161,7 +161,7 @@ struct ContentView: View {
     }
 
     private func installLocationUpdateHook() {
-        locationManager.onLocationUpdate = { [weak monitor] in
+        locationManager.onLocationUpdate = {
             self.updateAlertMonitor()
             // The Live Activity follows the same wake-ups — this hook
             // fires on every fix incl. background significant-change