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- FuelPriceFreshness is now station-level and display-only: one age per station, fresh/outdated/unknown/invalid, "May be outdated" past 30 days, with future-tolerance and non-finite guards.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- Copy reverted from "closest eligible station" to "closest station"; stale price-confidence strings removed, "May be outdated" added.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.

FuelBoardWidgets/FuelPriceWidget.swift

@@ -203,8 +203,6 @@ struct FuelPriceTimelineProvider<Configuration: WidgetConfigurationIntent & Widg
         // 3) Load + order stations per widget mode.
         let ordered: [FuelStation]
         var bestValueResult: FuelSavingsResult?
-        var bestValuePriceConfidence: FuelPriceFreshness.ComparisonConfidence = .ineligible
-        var bestValuePriceWarning: String?
         if isFavourites {
             let favourites = FuelStore.loadFavourites()
                 .filter { $0.station.prices[$0.fuel] != nil }
@@ -308,8 +306,7 @@ struct FuelPriceTimelineProvider<Configuration: WidgetConfigurationIntent & Widg
                     break
                 }
                 let amount = settings.preferredAmount
-                let baseline = FuelSavingsEstimator.bestValueBaselineStation(filtered, fuel: fuel,
-                                                                             journeyMiles: journey)
+                let baseline = FuelSavingsEstimator.baselineStation(filtered, fuel: fuel, journeyMiles: journey)
                 let ranked = FuelSavingsEstimator.ranked(
                     filtered,
                     fuel: fuel,
@@ -320,13 +317,6 @@ struct FuelPriceTimelineProvider<Configuration: WidgetConfigurationIntent & Widg
                 )
                 ordered = ranked
                 if let first = ranked.first, let baseline {
-                    bestValuePriceConfidence = FuelPriceFreshness.comparisonConfidence(
-                        station: first, fuel: fuel, baseline: baseline)
-                    bestValuePriceWarning = FuelPriceFreshness.comparisonWarning(
-                        station: first, fuel: fuel, baseline: baseline)
-                }
-                if let first = ranked.first, let baseline,
-                   bestValuePriceConfidence != .ineligible {
                     let baselineJourney = journey(baseline)
                     let result = FuelSavingsEstimator.availability(
                         station: first,
@@ -358,9 +348,7 @@ struct FuelPriceTimelineProvider<Configuration: WidgetConfigurationIntent & Widg
                 date: Date(), stations: Array(ordered.prefix(8)),
                 fuel: fuel, sort: sort, isFavourites: isFavourites,
                 location: origin, locationSource: source,
-                unit: unit, bestValueResult: bestValueResult,
-                bestValuePriceConfidence: bestValuePriceConfidence,
-                bestValuePriceWarning: bestValuePriceWarning
+                unit: unit, bestValueResult: bestValueResult
             )
         ), originSource)
     }