Live Activity: own fuel + distance config, independent of Stations tab

- Settings → Live Activity now has Fuel and Distance pickers (5/10/15,
  unit-aware) stored under fuelboard.liveActivityFuel / liveActivityRadiusMiles
- LiveActivityManager uses these instead of the Stations-tab selectedFuel /
  stationLimit; Stations changes no longer re-target the pill
- Fuel moved from Activity attributes into ContentState so changing fuel in
  Settings updates the RUNNING activity in place (no end+restart needed)
- Stations tab stays a pure data-interrogation + favourites surface

FuelBoard/LiveActivityManager.swift

@@ -48,6 +48,7 @@ enum LiveActivityManager {
         }
 
         let state = FuelBoardLiveActivityAttributes.ContentState(
+            fuel: fuel,
             stationID: best.id,
             stationName: best.name,
             brand: best.brand,
@@ -57,7 +58,7 @@ enum LiveActivityManager {
             lng: best.lng,
             updatedAt: Date()
         )
-        let attributes = FuelBoardLiveActivityAttributes(fuel: fuel)
+        let attributes = FuelBoardLiveActivityAttributes()
 
         if let current {
             // Near the 8 h cap? End and re-request so the pill keeps living.