Settings: concise copy and tighter hierarchy

Rewrite the Settings screen in short British English and remove the
duplicated paragraphs, keeping every control, binding and preference key as
it was.

- Fuel Savings: one-line descriptions for Best Value, average fuel economy,
  fill-up amount (worded for the unit in use) and minimum saving; one concise
  general explanation replaces the long footer; the orange "New comparison
  basis" notice is removed.
- Units: "Station sign" becomes "Pence per litre"; the combined paragraph
  becomes two contextual descriptions.
- Distances: "Accurate distances" becomes "Driving distances" with a short
  description; the route-request and search-radii paragraph is removed.
- Tap action: "Open map"/"More info" become "Directions"/"Station details"
  with a short description.
- Data checking: Standard and Smart summaries cut to one line each, one shared
  background-update note, duplicated footer removed.
- Replay onboarding: shorter description. Support FuelBoard untouched.

Copy and layout only: no calculations, ranking, refresh schedules, stored
values or persistence changed. New and reworded literals live in
FuelBoard/en.lproj/Localizable.strings.

Shared/FuelStore.swift

@@ -236,7 +236,7 @@ enum PriceDisplayStyle: String, Codable, CaseIterable, Identifiable {
 
     var displayName: String {
         switch self {
-        case .stationSign: return "Station sign"
+        case .stationSign: return "Pence per litre"
         case .poundsPence: return "Pounds & pence"
         }
     }
@@ -255,8 +255,8 @@ enum StationTapAction: String, Codable, CaseIterable, Identifiable {
 
     var displayName: String {
         switch self {
-        case .openMap: return "Open map"
-        case .showDetails: return "More info"
+        case .openMap: return "Directions"
+        case .showDetails: return "Station details"
         }
     }
 }