Make station price age informational only

The relay's price_updated is the maximum price_last_updated across the grades it maps, so it cannot vouch for the selected grade: stop using it to score, gate or warn about Best Value.

- FuelPriceFreshness is now station-level and display-only: one age per station, fresh/outdated/unknown/invalid, "May be outdated" past 30 days, with future-tolerance and non-finite guards.
- Best Value restores the closest-station-selling-the-selected-fuel baseline and its savings ranking; eligibility gating, eligible-first sorting and the unavailable banner are gone.
- Price age appears in the More info sheet only - no listing-row warnings, no extra banners.
- Copy reverted from "closest eligible station" to "closest station"; stale price-confidence strings removed, "May be outdated" added.
- Dormant per-grade timestamp plumbing removed, and regression tests added for every fuel type, missing/invalid/future stamps and the bundled offline dump.

FuelBoard/ContentView.swift

@@ -401,9 +401,9 @@ struct ContentView: View {
     /// (computing a journey for each) and `savingsLookup` immediately scanned them
     /// all AGAIN to fill the per-station map. Both now share one result.
     ///
-    /// The baseline is chosen with the same journey and selected-fuel freshness
-    /// guards as `FuelSavingsEstimator.bestValueBaselineStation` when configured;
-    /// with the feature off, the ordinary Closest station still names that row.
+    /// The baseline is chosen with the same journey guards as
+    /// `FuelSavingsEstimator.baselineStation` when configured; with the feature
+    /// off, the ordinary Closest station still names that row.
     private func savingsScaffold() -> (baseline: FuelStation?, journeys: [String: FuelSavingsJourney]) {
         guard let location else { return (nil, [:]) }
         guard fuelSavingsSettings.isConfigured else {
@@ -418,7 +418,7 @@ struct ContentView: View {
                 journeys[station.id] = journey
             }
         }
-        let baseline = FuelSavingsEstimator.bestValueBaselineStation(stations, fuel: selectedFuel) {
+        let baseline = FuelSavingsEstimator.baselineStation(stations, fuel: selectedFuel) {
             journeys[$0.id]
         }
         return (baseline, journeys)
@@ -454,15 +454,15 @@ struct ContentView: View {
         }
     }
 
-    /// The Closest station with an eligible selected-fuel price — the Best Value
-    /// comparison baseline. Ordinary Closest sorting still includes stale stations.
-    /// It uses the same journey values as the savings calculation, so a cached
-    /// road route can change the baseline and keep the "extra return travel"
-    /// labels synchronized with the cost calculation. Without a cached route,
-    /// the journey falls back to straight-line and the result is an estimate.
+    /// The nearest station that sells the selected fuel — the Best Value
+    /// comparison baseline. It is chosen with the SAME journey values used by
+    /// the savings calculation, so a cached road route can change the baseline
+    /// and keep the "extra return travel" labels synchronized with the
+    /// cost calculation. When no road route is cached, the journey falls back to
+    /// straight-line out-and-back, and the result is marked as an estimate.
     private var nearestSavingsBaseline: FuelStation? {
         guard let location else { return nil }
-        return FuelSavingsEstimator.bestValueBaselineStation(
+        return FuelSavingsEstimator.baselineStation(
             stations,
             fuel: selectedFuel,
             journeyMiles: { [self] station in savingsJourneyMiles(for: station, location: location) }
@@ -802,10 +802,6 @@ struct ContentView: View {
                         fuelSavings: savingsLookup(baseline: scaffold.baseline,
                                                    journeys: scaffold.journeys)(station),
                         fuelSavingsAmount: sessionFuelSavingsAmount,
-                        savingsPriceConfidence: FuelPriceFreshness.ComparisonConfidence.assess(
-                            station: station, fuel: selectedFuel, baseline: scaffold.baseline),
-                        savingsPriceWarning: FuelPriceFreshness.comparisonWarning(
-                            station: station, fuel: selectedFuel, baseline: scaffold.baseline),
                         savingsBaselineStationName: scaffold.baseline?.name,
                         journeyDiagnostics: journeyDiagnostics(for: station, baseline: scaffold.baseline),
                         isFavourite: favouriteIDs.contains(station.id),
@@ -1532,12 +1528,6 @@ struct ContentView: View {
             fuelSavingsAmount: $sessionFuelSavingsAmount,
             savingsForStation: savingsLookup(baseline: baselineStation, journeys: scaffold.journeys),
             journeyDiagnosticsForStation: { station in journeyDiagnostics(for: station, baseline: baselineStation) },
-            savingsPriceConfidenceForStation: { station in
-                FuelPriceFreshness.ComparisonConfidence.assess(station: station, fuel: selectedFuel, baseline: baselineStation)
-            },
-            savingsPriceWarningForStation: { station in
-                FuelPriceFreshness.comparisonWarning(station: station, fuel: selectedFuel, baseline: baselineStation)
-            },
             onToggleFavourite: toggleFavourite,
             onRefresh: { await refresh(force: true) }
         )
@@ -1559,12 +1549,6 @@ struct ContentView: View {
             fuelSavingsAmount: $sessionFuelSavingsAmount,
             savingsForStation: savingsLookup(baseline: baselineStation, journeys: scaffold.journeys),
             journeyDiagnosticsForStation: { station in journeyDiagnostics(for: station, baseline: baselineStation) },
-            savingsPriceConfidenceForStation: { station in
-                FuelPriceFreshness.ComparisonConfidence.assess(station: station, fuel: selectedFuel, baseline: baselineStation)
-            },
-            savingsPriceWarningForStation: { station in
-                FuelPriceFreshness.comparisonWarning(station: station, fuel: selectedFuel, baseline: baselineStation)
-            },
             onToggleFavourite: toggleFavourite,
             onReorder: reorderFavourites,
             onHistoryUnavailable: { if dataStatus == .live { dataStatus = .connectionProblem } },
@@ -1802,8 +1786,6 @@ struct StationRow: View {
     /// compact banner does not print it today, but a row that carried a hard
     /// zero would print "for £0" the moment it did — pass the real figure.
     var fuelSavingsAmount: FuelSavingsFillAmount = FuelSavingsSettings.defaultPreferredAmount
-    var savingsPriceConfidence: FuelPriceFreshness.ComparisonConfidence = .ineligible
-    var savingsPriceWarning: String? = nil
     var onToggleFavourite: () -> Void = {}
     var onShowDetails: (FuelStation) -> Void = { _ in }
 
@@ -1964,8 +1946,6 @@ struct StationRow: View {
                 FuelSavingsSummaryView(
                     availability: fuelSavings,
                     amount: fuelSavingsAmount,
-                    priceConfidence: savingsPriceConfidence,
-                    priceWarning: savingsPriceWarning,
                     compact: true,
                     distanceUnit: distanceUnit
                 )