Add Smart data checking mode

FuelBoard/SettingsView.swift

@@ -18,6 +18,7 @@ struct SettingsView: View {
     @ObservedObject var tipStore: TipStore
     @Binding var distanceUnit: DistanceUnit
     @Binding var priceDisplayStyle: PriceDisplayStyle
+    @Binding var dataRefreshMode: DataRefreshMode
     /// The fuel + radius currently configured for alerts (mirrors the Alerts
     /// tab) so the test notification matches what real alerts will say.
     var alertsFuel: FuelType = .e10
@@ -120,6 +121,29 @@ struct SettingsView: View {
                     Text("Distances and search radii across the app, widget and alerts are shown in this unit. Prices can be shown as on a station sign (129.9) or in pounds and pence (£1.29⁹/L).")
                 }
 
+                Section {
+                    Picker("Data checking", selection: $dataRefreshMode) {
+                        ForEach(DataRefreshMode.allCases) { mode in
+                            Text(mode.displayName).tag(mode)
+                        }
+                    }
+                    .pickerStyle(.segmented)
+                    .onChange(of: dataRefreshMode) { _, newValue in
+                        FuelStore.saveDataRefreshMode(newValue)
+                        SmartDataRefreshScheduler.scheduleNextIfNeeded()
+                    }
+                    VStack(alignment: .leading, spacing: 8) {
+                        Text(dataRefreshMode.summary)
+                        Text("Background checks are best-effort and happen only when iOS allows, so timing is not exact.")
+                            .foregroundStyle(.secondary)
+                    }
+                    .font(.footnote)
+                } header: {
+                    Text("Data checking")
+                } footer: {
+                    Text("Standard saves battery and refreshes price data up to twice daily. Smart checks for newer data more often in the background and only refreshes full prices when an update is available.")
+                }
+
                 Section {
                     Button {
                         onShowOnboarding()