Settings: price display toggle — station sign (£129.9) vs pounds & pence (£1.299); display-only, all surfaces (list, widgets, Live Activity, Siri cards); Siri dialog stays speech-safe pounds

Shared/FuelStore.swift

@@ -143,6 +143,25 @@ enum DistanceUnit: String, Codable, CaseIterable, Identifiable {
     }
 }
 
+/// Display style for fuel prices. Internally prices are always stored and
+/// computed in pence-per-litre (GOV.UK's unit, e.g. 129.9); the style only
+/// affects RENDERING: the station-sign convention shows the pence figure
+/// ("£129.9", what a forecourt sign shows), pounds & pence shows the
+/// converted value ("£1.299"). Calculations never see this.
+enum PriceDisplayStyle: String, Codable, CaseIterable, Identifiable {
+    case stationSign   // £129.9 — matches the sign
+    case poundsPence   // £1.299
+
+    var id: String { rawValue }
+
+    var displayName: String {
+        switch self {
+        case .stationSign: return "Station sign (£129.9)"
+        case .poundsPence: return "Pounds & pence (£1.299)"
+        }
+    }
+}
+
 // MARK: - Station model
 
 struct FuelStation: Identifiable, Codable, Equatable {
@@ -435,6 +454,40 @@ struct FuelStore {
         saveString(unit.rawValue, service: distanceUnitKey)
     }
 
+    // MARK: Price display — station-sign (£129.9) vs pounds & pence (£1.299).
+    // Prices are always stored/computed in pence-per-litre; this style only
+    // changes how they are RENDERED, so it can never affect calculations.
+    // Default station sign = the forecourt convention.
+
+    static let priceDisplayStyleKey = "fuelboard.priceDisplayStyle"
+
+    static func loadPriceDisplayStyle() -> PriceDisplayStyle {
+        if let raw = loadString(service: priceDisplayStyleKey), let style = PriceDisplayStyle(rawValue: raw) {
+            return style
+        }
+        return .stationSign
+    }
+
+    static func savePriceDisplayStyle(_ style: PriceDisplayStyle) {
+        saveString(style.rawValue, service: priceDisplayStyleKey)
+    }
+
+    /// Render a pence-per-litre price per the saved style:
+    /// stationSign -> "£129.9" (sign convention), poundsPence -> "£1.299".
+    static func priceText(_ pence: Double, style: PriceDisplayStyle? = nil) -> String {
+        switch style ?? loadPriceDisplayStyle() {
+        case .stationSign: return String(format: "£%.1f", pence)
+        case .poundsPence: return String(format: "£%.3f", pence / 100)
+        }
+    }
+
+    /// Speech-safe pounds form for Siri dialogs — Siri would read "£129.9"
+    /// aloud as "one hundred and twenty-nine pounds", so the SPOKEN answer
+    /// always uses pounds regardless of the display style.
+    static func priceTextSpoken(_ pence: Double) -> String {
+        String(format: "£%.3f", pence / 100)
+    }
+
     // MARK: Debug mode
 
     /// Hidden developer flag. NOT exposed in the UI: toggled by tapping the