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

Shared/FuelBoardLiveActivity.swift

@@ -5,20 +5,21 @@
 // is deliberately NOT symlinked into FuelBoardTests/Sources — the SPM test
 // target runs on macOS where ActivityKit does not exist.
 //
-// The activity mirrors the app's TOP badge: the cheapest station selling the
-// app's selected fuel within the app's chosen distance radius. Tapping the
-// activity opens Apple Maps driving directions to that station (maps://).
+// The activity tracks the cheapest station for the fuel + radius configured
+// in Settings → Live Activity (INDEPENDENT of the Stations-tab selection).
+// Everything dynamic lives in ContentState so updates — including a fuel
+// change — apply to the running activity without needing to restart it.
+// Tapping the activity opens Apple Maps driving directions (maps://).
 
 import ActivityKit
 import Foundation
 
-/// Attributes are fixed at request time. Here they pin the FUEL being
-/// tracked; everything that can change while driving (station, price,
-/// distance) lives in ContentState so updates don't need a new activity.
+/// Attributes are fixed at request time. Kept empty: the fuel itself lives in
+/// ContentState so a fuel change in Settings updates the running activity
+/// in place instead of requiring an end + restart.
 struct FuelBoardLiveActivityAttributes: ActivityAttributes {
-    var fuel: FuelType
-
     public struct ContentState: Codable, Hashable {
+        var fuel: FuelType
         var stationID: String
         var stationName: String
         var brand: String

Shared/FuelStore.swift

@@ -263,6 +263,8 @@ struct FuelStore {
     static let alertsFuelKey = "fuelboard.alertsFuel"       // FuelType raw value
     static let debugModeKey = "fuelboard.debugMode"         // Bool — hidden dev flag
     static let liveActivityKey = "fuelboard.liveActivity"    // Bool — Live Activity toggle
+    static let liveActivityFuelKey = "fuelboard.liveActivityFuel"    // FuelType raw value
+    static let liveActivityRadiusKey = "fuelboard.liveActivityRadiusMiles" // Int miles (5/10/15)
     static let onboardingCompletedKey = "fuelboard.onboardingCompleted" // Bool
     static let lastRefreshKey = "fuelboard.lastRefresh"      // TimeInterval (seconds since 1970)
     static let relaySourceKey = "fuelboard.relaySource"      // String — "api" | "csv"
@@ -501,6 +503,32 @@ struct FuelStore {
         saveString(enabled ? "1" : "0", service: liveActivityKey)
     }
 
+    /// The fuel the Live Activity tracks — independent of the Stations-tab
+    /// selection so the Lock Screen pill keeps its own target.
+    static func loadLiveActivityFuel() -> FuelType {
+        if let raw = loadString(service: liveActivityFuelKey), let fuel = FuelType(rawValue: raw) {
+            return fuel
+        }
+        return .e10
+    }
+
+    static func saveLiveActivityFuel(_ fuel: FuelType) {
+        saveString(fuel.rawValue, service: liveActivityFuelKey)
+    }
+
+    /// The Live Activity's search radius in miles (5/10/15), converted to the
+    /// chosen unit at use — same options as the Stations list.
+    static func loadLiveActivityRadiusMiles() -> Int {
+        if let raw = loadString(service: liveActivityRadiusKey), let value = Int(raw), stationRadiusOptions.contains(value) {
+            return value
+        }
+        return 5
+    }
+
+    static func saveLiveActivityRadiusMiles(_ miles: Int) {
+        saveString(String(miles), service: liveActivityRadiusKey)
+    }
+
     // MARK: Refresh policy — data is cached; the app only auto-refreshes
     // twice a day (pull-to-refresh is the manual override).