Cache-first refresh policy: auto-fetch at most twice a day (12h gate), no fetch on launch/foreground/location/fuel-switch, pull-to-refresh forces; geofences still follow location

FuelBoard/StationsView.swift

@@ -14,6 +14,7 @@ struct StationsView: View {
     let radiusKM: Double
     let favouriteIDs: Set<String>
     var onToggleFavourite: (FuelStation) -> Void = { _ in }
+    var onRefresh: () async -> Void = {}
 
     var body: some View {
         NavigationStack {
@@ -130,6 +131,10 @@ struct StationsView: View {
                     }
                 }
             }
+            .refreshable {
+                // Manual override for the twice-a-day cache policy.
+                await onRefresh()
+            }
             .navigationTitle("FuelBoard")
         }
     }