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/ContentView.swift

@@ -21,6 +21,7 @@ struct ContentView: View {
     @State private var stationLimit: Int = FuelStore.loadStationLimit()
     @State private var distanceUnit: DistanceUnit = FuelStore.loadDistanceUnit()
     @State private var priceDisplayStyle: PriceDisplayStyle = FuelStore.loadPriceDisplayStyle()
+    @State private var stationTapAction: StationTapAction = FuelStore.loadStationTapAction()
     @State private var favourites: [FavouriteEntry] = FuelStore.loadFavourites()
     @State private var alertsEnabled: Bool = FuelStore.loadAlertsEnabled()
     @State private var alertsRadius: Double = FuelStore.loadAlertsRadius()
@@ -742,6 +743,7 @@ struct ContentView: View {
             topStationID: topStationID,
             location: location,
             favouriteIDs: favouriteIDs,
+            stationTapAction: stationTapAction,
             onToggleFavourite: toggleFavourite,
             onRefresh: { await refresh(force: true) }
         )
@@ -756,6 +758,7 @@ struct ContentView: View {
             location: location,
             distanceUnit: distanceUnit,
             priceDisplayStyle: priceDisplayStyle,
+            stationTapAction: stationTapAction,
             onToggleFavourite: toggleFavourite,
             onReorder: reorderFavourites,
             onHistoryUnavailable: { if dataStatus == .live { dataStatus = .connectionProblem } },
@@ -794,6 +797,7 @@ struct ContentView: View {
             tipStore: tipStore,
             distanceUnit: $distanceUnit,
             priceDisplayStyle: $priceDisplayStyle,
+            stationTapAction: $stationTapAction,
             dataRefreshMode: $dataRefreshMode,
             alertsFuel: alertsFuel,
             alertsRadiusKM: alertsRadius,
@@ -931,7 +935,9 @@ struct StationRow: View {
     let baselinePrice: Double?
     let isTopResult: Bool
     let isFavourite: Bool
+    var tapAction: StationTapAction = .openMap
     var onToggleFavourite: () -> Void = {}
+    var onShowDetails: (FuelStation) -> Void = { _ in }
 
     private var ragColor: Color {
         guard let price = station.prices[fuel], let baselinePrice else { return .gray }
@@ -1030,8 +1036,13 @@ struct StationRow: View {
         }
         .contentShape(Rectangle())
         .onTapGesture {
-            if let url = station.mapsDirectionsURL {
-                UIApplication.shared.open(url)
+            switch tapAction {
+            case .openMap:
+                if let url = station.mapsDirectionsURL {
+                    UIApplication.shared.open(url)
+                }
+            case .showDetails:
+                onShowDetails(station)
             }
         }
     }