Live Activity: cheapest-in-radius Lock Screen/Dynamic Island pill

- Shared FuelBoardLiveActivityAttributes/ContentState (app + widget targets)
- FuelBoardLiveActivity Widget: ActivityConfiguration rendered by the widget
  extension - Lock Screen banner + Dynamic Island (leading/trailing/bottom,
  compact, minimal), tap anywhere -> maps:// directions to the best station
- LiveActivityManager (app side): request/update/end; mirrors the app list's
  TOP badge (selected fuel + chosen distance radius, price-then-distance
  ties); local start-date tracking for the 8h cap (this SDK's Activity has no
  startDate) - auto-restarts at 7h59m; silent no-op when disabled/denied
- Wiring: 250m/60s location hook (incl. background significant-change
  wake-ups), refresh completion, fuel/radius/unit changes, toggle flip
- Settings toggle + FuelStore persistence (keychain-backed, app-group)
- App-Info.plist: NSSupportsLiveActivities

FuelBoard/ContentView.swift

@@ -14,6 +14,7 @@ struct ContentView: View {
     @State private var alertsEnabled: Bool = FuelStore.loadAlertsEnabled()
     @State private var alertsRadius: Double = FuelStore.loadAlertsRadius()
     @State private var alertsFuel: FuelType = FuelStore.loadAlertsFuel()
+    @State private var liveActivityEnabled: Bool = FuelStore.loadLiveActivityEnabled()
     @State private var location: Coordinate? = {
         if let loc = FuelStore.loadLocation() { return Coordinate(lat: loc.lat, lng: loc.lng) }
         return nil
@@ -188,10 +189,15 @@ struct ContentView: View {
                 locationManager.onLocationUpdate = { [weak monitor] in
                     monitor?.update(stations: stations, favourites: refreshedFavourites,
                                     fuel: alertsFuel, radiusKM: alertsRadius)
+                    // The Live Activity follows the same wake-ups — this hook
+                    // fires on every fix incl. background significant-change
+                    // wake-ups, so the Lock Screen pill stays live while driving.
+                    updateLiveActivity()
                 }
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: alertsRadius)
                 monitor.setEnabled(alertsEnabled)
+                updateLiveActivity()
                 // Refresh only when the cache is stale (twice-a-day policy).
                 Task { await refresh() }
             } else {
@@ -210,6 +216,7 @@ struct ContentView: View {
                 locationManager.startForegroundTracking()
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: alertsRadius)
+                updateLiveActivity()
                 Task { await refresh(force: true) }
             }
         }
@@ -223,6 +230,7 @@ struct ContentView: View {
                 }
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: alertsRadius)
+                updateLiveActivity()
                 // No network fetch on foreground — pull-to-refresh is the override.
             } else {
                 locationManager.stopForegroundTracking()
@@ -237,11 +245,13 @@ struct ContentView: View {
                 // NOT re-fetched on every movement (cached, twice-a-day policy).
                 monitor.update(stations: stations, favourites: refreshedFavourites,
                                fuel: alertsFuel, radiusKM: alertsRadius)
+                updateLiveActivity()
             }
         }
         .onChange(of: selectedFuel) { _, _ in
             // No re-fetch needed — one response carries E5/E10/DIESEL prices.
             WidgetCenter.shared.reloadAllTimelines()
+            updateLiveActivity()
         }
         .onChange(of: stationLimit) { _, newValue in
             // Distance filter is LOCAL math now — the cache holds the full-UK
@@ -250,6 +260,7 @@ struct ContentView: View {
             // next render.
             FuelStore.saveStationLimit(newValue)
             WidgetCenter.shared.reloadAllTimelines()
+            updateLiveActivity()
         }
         .onChange(of: alertsEnabled) { _, newValue in
             FuelStore.saveAlertsEnabled(newValue)
@@ -272,6 +283,31 @@ struct ContentView: View {
             monitor.update(stations: stations, favourites: refreshedFavourites,
                            fuel: newValue, radiusKM: alertsRadius)
         }
+        .onChange(of: liveActivityEnabled) { _, newValue in
+            // Toggling the Live Activity on starts it with the current best
+            // station; toggling off ends any running activity.
+            FuelStore.saveLiveActivityEnabled(newValue)
+            updateLiveActivity()
+        }
+        .onChange(of: distanceUnit) { _, _ in
+            // Distance unit changes the radius — mirror the new radius in the
+            // Live Activity immediately.
+            updateLiveActivity()
+        }
+    }
+
+    /// Pushes the current best-in-radius station into the Live Activity.
+    /// No-op (or ends the activity) when the toggle is off or there's no
+    /// location/data yet. Mirrors the app list's TOP badge: selected fuel +
+    /// chosen distance radius, cheapest then nearest on ties.
+    private func updateLiveActivity() {
+        LiveActivityManager.update(
+            stations: stations,
+            fuel: selectedFuel,
+            radiusKM: distanceUnit.toKM(Double(stationLimit)),
+            location: location,
+            enabled: liveActivityEnabled
+        )
     }
 
     /// The Settings tab, extracted from `body` so the TabView expression stays
@@ -279,6 +315,7 @@ struct ContentView: View {
     private var settingsTab: some View {
         SettingsView(
             distanceUnit: $distanceUnit,
+            liveActivityEnabled: $liveActivityEnabled,
             alertsFuel: alertsFuel,
             alertsRadiusKM: alertsRadius,
             testAlertResult: monitor.lastTestResult,
@@ -342,6 +379,8 @@ struct ContentView: View {
         // Keep monitor geofences in sync with the freshest data.
         monitor.update(stations: stations, favourites: refreshedFavourites,
                        fuel: alertsFuel, radiusKM: alertsRadius)
+        // Fresh prices → refresh the Live Activity pill too.
+        updateLiveActivity()
     }
 }