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- FuelPriceFreshness is now station-level and display-only: one age per station, fresh/outdated/unknown/invalid, "May be outdated" past 30 days, with future-tolerance and non-finite guards.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- Copy reverted from "closest eligible station" to "closest station"; stale price-confidence strings removed, "May be outdated" added.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

@@ -80,9 +80,6 @@ struct FuelSavingsAdjustmentView: View {
 struct FuelSavingsSummaryView: View {
     let availability: FuelSavingsAvailability?
     let amount: FuelSavingsFillAmount
-    /// Candidate/baseline price confidence for every Best Value result.
-    var priceConfidence: FuelPriceFreshness.ComparisonConfidence = .ineligible
-    var priceWarning: String? = nil
     var baselineStationName: String? = nil
     var compact: Bool = false
     /// Sizes the "extra return travel" caption in the user's own unit (the
@@ -120,12 +117,6 @@ struct FuelSavingsSummaryView: View {
                         .lineLimit(1)
                         .minimumScaleFactor(0.85)
                         .accessibilityLabel("Comparison: \(comparisonLabel(for: result))")
-                    if let warning = priceWarning ?? priceConfidence.warningText {
-                        Text(warning)
-                            .font(.caption2)
-                            .foregroundStyle(.orange)
-                            .accessibilityLabel(warning)
-                    }
                     if let extraTravel = FuelSavingsFormat.extraTravelLabel(
                         extraDistanceMiles: result.extraDistanceMiles,
                         unit: distanceUnit,
@@ -166,16 +157,10 @@ struct FuelSavingsSummaryView: View {
                     LabeledContent("Fuel you'll receive", value: String(format: "%.2f litres", result.fillLitres))
                         .monospacedDigit()
                     if amount.unit == .pounds {
-                        Text("You pay the selected budget here. The saving compares the same litres at your closest eligible station; litres differ between stations, and this is not a refund.")
+                        Text("You pay the selected budget here. The saving compares the same litres at your closest station; litres differ between stations, and this is not a refund.")
                             .font(.caption2)
                             .foregroundStyle(.secondary)
                     }
-                    if let warning = priceWarning ?? priceConfidence.warningText {
-                        Text(warning)
-                            .font(.caption2)
-                            .foregroundStyle(.orange)
-                            .accessibilityLabel(warning)
-                    }
                     if let extraTravel = FuelSavingsFormat.extraTravelLabel(
                         extraDistanceMiles: result.extraDistanceMiles,
                         unit: distanceUnit,
@@ -187,11 +172,11 @@ struct FuelSavingsSummaryView: View {
                             .accessibilityLabel(spokenExtraTravel(for: result, fallback: extraTravel))
                     }
                     if result.status == .baseline {
-                        Text("Your closest eligible station by journey distance is the baseline — every other saving is measured against it.")
+                        Text("Your closest station by journey distance is the baseline — every other saving is measured against it.")
                             .font(.caption)
                             .foregroundStyle(.secondary)
                     } else {
-                        Text(baselineStationName.map { "Compared with \($0)." } ?? "Compared with your closest eligible station.")
+                        Text(baselineStationName.map { "Compared with \($0)." } ?? "Compared with your closest station.")
                             .font(.caption)
                             .foregroundStyle(.secondary)
                         LabeledContent(
@@ -266,8 +251,8 @@ struct FuelSavingsSummaryView: View {
     }
 
     /// VoiceOver form of the verdict. `spokenHeadline()` spells "Approx." out for
-    /// and leaves the plain words ("Break even", "Closest eligible
-    /// station") alone — one source, so visible and spoken copy cannot drift.
+    /// and leaves the plain words ("Break even", "Closest station") alone —
+    /// one source, so visible and spoken copy cannot drift.
     private func accessibilityHeadline(for result: FuelSavingsResult) -> String {
         result.spokenHeadline()
     }