Copy: England → UK-wide, include Northern Ireland; migrate user-facing copy into Localizable.strings

- Onboarding feature: 'England-wide prices' → 'UK-wide prices — 8,000+ stations, updated twice a day' (key + value unified)
- Stations empty state: 'covers England, Scotland and Wales' → 'covers the whole UK' (dataset includes Northern Ireland)
- Settings Data source footer: source wording updated (CSV mirror or API), OGL attribution retained
- Empty state, browse button and OGL footer now keys in Localizable.strings so the web copy editor covers them
- APPSTORE.md + BACKLOG.md + code comments: England-wide → UK-wide, NI included

FuelBoard/StationsView.swift

@@ -104,9 +104,9 @@ struct StationsView: View {
                         let miles = distanceUnit.displayMiles(stationLimit)
                         let unit = distanceUnit.label(for: Double(miles))
                         VStack(alignment: .leading, spacing: 6) {
-                            Text("No \(selectedFuel.displayName) stations within \(miles) \(unit).")
+                            Text(String(format: NSLocalizedString("No %@ stations within %lld %@.", comment: "Empty state when the radius finds nothing nearby"), selectedFuel.displayName, miles, unit))
                                 .foregroundStyle(.secondary)
-                            Text("FuelBoard covers England, Scotland and Wales — try Closest to browse every UK station.")
+                            Text("FuelBoard covers the whole UK — try Closest to browse every station.")
                                 .font(.caption)
                                 .foregroundStyle(.secondary)
                             Button("Browse all UK stations") {