Best Value: explain price age per surface instead of one blanket warning

- Station detail now separates the station's own report age from the
  selected fuel's update time, so a recent station-wide report no longer
  reads as an old price.
- Warning copy names the fuel and says which side is weak: the station's
  price is not individually dated, or the baseline's is. The misleading
  "unverified or older than 7 days" line is gone.
- Wording stays "Closest" throughout; new copy uses Unleaded / Premium /
  Diesel rather than the internal grade codes.
- Localisation: new and updated keys for the added copy.

FuelBoard/FavouritesView.swift

@@ -25,6 +25,8 @@ struct FavouritesView: View {
     /// journey distance — the same baseline and definition the Stations list uses.
     var savingsForStation: (FuelStation) -> FuelSavingsAvailability? = { _ in nil }
     var journeyDiagnosticsForStation: (FuelStation) -> FuelSavingsJourneyDiagnostics? = { _ in nil }
+    var savingsPriceConfidenceForStation: (FuelStation) -> FuelPriceFreshness.ComparisonConfidence
+    var savingsPriceWarningForStation: (FuelStation) -> String? = { _ in nil }
     var onToggleFavourite: (FuelStation, FuelType) -> Void = { _, _ in }
     /// Persists a reordered favourites array (after drag-and-drop).
     var onReorder: ([FavouriteEntry]) -> Void = { _ in }
@@ -84,6 +86,8 @@ struct FavouritesView: View {
          fuelSavingsAmount: Binding<FuelSavingsFillAmount>,
          savingsForStation: @escaping (FuelStation) -> FuelSavingsAvailability? = { _ in nil },
          journeyDiagnosticsForStation: @escaping (FuelStation) -> FuelSavingsJourneyDiagnostics? = { _ in nil },
+         savingsPriceConfidenceForStation: @escaping (FuelStation) -> FuelPriceFreshness.ComparisonConfidence = { _ in .ineligible },
+         savingsPriceWarningForStation: @escaping (FuelStation) -> String? = { _ in nil },
          onToggleFavourite: @escaping (FuelStation, FuelType) -> Void = { _, _ in },
          onReorder: @escaping ([FavouriteEntry]) -> Void = { _ in },
          onHistoryUnavailable: (() -> Void)? = nil,
@@ -98,6 +102,8 @@ struct FavouritesView: View {
         _fuelSavingsAmount = fuelSavingsAmount
         self.savingsForStation = savingsForStation
         self.journeyDiagnosticsForStation = journeyDiagnosticsForStation
+        self.savingsPriceConfidenceForStation = savingsPriceConfidenceForStation
+        self.savingsPriceWarningForStation = savingsPriceWarningForStation
         self.onToggleFavourite = onToggleFavourite
         self.onReorder = onReorder
         self.onHistoryUnavailable = onHistoryUnavailable
@@ -144,10 +150,7 @@ struct FavouritesView: View {
 
                     if fuelSavingsSettings.isConfigured {
                         Section {
-                            FuelSavingsAdjustmentView(
-                                amount: $fuelSavingsAmount,
-                                referencePricePencePerLitre: cheapestPrice
-                            )
+                            FuelSavingsAdjustmentView(amount: $fuelSavingsAmount)
                         } footer: {
                             Text(String(localized: "Savings below are estimated against the closest eligible station by journey distance — the same baseline as the Stations list.", comment: "Favourites fuel-savings explanation"))
                         }
@@ -168,6 +171,8 @@ struct FavouritesView: View {
                                 tapAction: stationTapAction,
                                 fuelSavings: savingsForStation(station),
                                 fuelSavingsAmount: fuelSavingsAmount,
+                                savingsPriceConfidence: savingsPriceConfidenceForStation(station),
+                                savingsPriceWarning: savingsPriceWarningForStation(station),
                                 onToggleFavourite: { onToggleFavourite(station, activeFuel) },
                                 onShowDetails: { detailStation = $0 }
                             )
@@ -216,8 +221,11 @@ struct FavouritesView: View {
                     station: station,
                     location: location,
                     distanceUnit: distanceUnit,
+                    selectedFuel: activeFuel,
                     fuelSavings: savingsForStation(station),
                     fuelSavingsAmount: fuelSavingsAmount,
+                    savingsPriceConfidence: savingsPriceConfidenceForStation(station),
+                    savingsPriceWarning: savingsPriceWarningForStation(station),
                     journeyDiagnostics: journeyDiagnosticsForStation(station),
                     // Every station listed here IS a favourite for the tab's
                     // fuel, so the star starts filled; tapping it unstars.