Tabs (Stations/Favourites/Alerts): favourites with cheapest-first ranking, proximity geofence alerts (favourites priority, 3km default radius, 1h dedup), Always location + background mode

Shared/FuelStore.swift

@@ -127,6 +127,9 @@ struct FuelStore {
     static let fuelKey = "fuelboard.selectedFuel"      // FuelType raw value
     static let sortModeKey = "fuelboard.sortMode"      // SortMode raw value
     static let stationLimitKey = "fuelboard.stationLimit" // Int (10/25/50/75/100)
+    static let favouritesKey = "fuelboard.favourites"      // [FuelStation] JSON
+    static let alertsEnabledKey = "fuelboard.alertsEnabled" // Bool
+    static let alertsRadiusKey = "fuelboard.alertsRadius"   // Double km
 
     // MARK: Stations
 
@@ -204,6 +207,61 @@ struct FuelStore {
         saveString(String(limit), service: stationLimitKey)
     }
 
+    // MARK: Favourites
+
+    static func loadFavourites() -> [FuelStation] {
+        if let data = keychainData(service: favouritesKey),
+           let favs = try? JSONDecoder().decode([FuelStation].self, from: data) {
+            return favs
+        }
+        if let defaults = UserDefaults(suiteName: appGroupSuite),
+           let data = defaults.data(forKey: favouritesKey),
+           let favs = try? JSONDecoder().decode([FuelStation].self, from: data) {
+            return favs
+        }
+        return []
+    }
+
+    static func saveFavourites(_ favourites: [FuelStation]) {
+        if let data = try? JSONEncoder().encode(favourites) {
+            UserDefaults(suiteName: appGroupSuite)?.set(data, forKey: favouritesKey)
+            writeKeychain(data: data, service: favouritesKey)
+        }
+    }
+
+    /// Returns favourites with fresh prices applied from the given station list
+    /// (favourites keep their cached snapshot when not in the current results).
+    static func refreshedFavourites(_ favourites: [FuelStation], from stations: [FuelStation]) -> [FuelStation] {
+        var updated = favourites
+        for (i, fav) in favourites.enumerated() {
+            if let fresh = stations.first(where: { $0.id == fav.id }) {
+                updated[i] = fresh
+            }
+        }
+        return updated
+    }
+
+    // MARK: Alerts
+
+    static func loadAlertsEnabled() -> Bool {
+        loadString(service: alertsEnabledKey) == "1"
+    }
+
+    static func saveAlertsEnabled(_ enabled: Bool) {
+        saveString(enabled ? "1" : "0", service: alertsEnabledKey)
+    }
+
+    static func loadAlertsRadius() -> Double {
+        if let raw = loadString(service: alertsRadiusKey), let value = Double(raw), value >= 1, value <= 10 {
+            return value
+        }
+        return 3.0
+    }
+
+    static func saveAlertsRadius(_ radius: Double) {
+        saveString(String(radius), service: alertsRadiusKey)
+    }
+
     // MARK: Low-level keychain helpers
 
     private static func keychainData(service: String) -> Data? {