feat: station tap action toggle (open map vs more info)

Settings → Units gains a Tap station picker: Open map (default,
historic behaviour — tap opens Apple Maps directions) or More info
(tap shows a detail sheet with name, address, distance from current
location, and a Directions button). Applies to Stations and
Favourites tabs; persisted keychain-first as
fuelboard.stationTapAction. Stations footer hint follows the setting.

FuelBoard/SettingsView.swift

@@ -18,6 +18,7 @@ struct SettingsView: View {
     @ObservedObject var tipStore: TipStore
     @Binding var distanceUnit: DistanceUnit
     @Binding var priceDisplayStyle: PriceDisplayStyle
+    @Binding var stationTapAction: StationTapAction
     @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.
@@ -117,10 +118,19 @@ struct SettingsView: View {
                         WidgetCenter.shared.reloadAllTimelines()
                         WatchSyncManager.shared.pushSnapshot()
                     }
+                    Picker("Tap station", selection: $stationTapAction) {
+                        ForEach(StationTapAction.allCases) { action in
+                            Text(action.displayName).tag(action)
+                        }
+                    }
+                    .pickerStyle(.segmented)
+                    .onChange(of: stationTapAction) { _, newValue in
+                        FuelStore.saveStationTapAction(newValue)
+                    }
                 } header: {
                     Text("Units")
                 } footer: {
-                    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).")
+                    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). Tapping a station either opens directions straight away or shows its details first.")
                 }
 
                 Section {