Widget preview screen + shared widget rendering; dark-mode screenshots with real data

- Move widget entry view into Shared/FuelPriceWidgetViews.swift (FuelPriceWidgetContent,
  FuelPriceWidgetEntryData) so the app can render the REAL widget faces; widget
  extension now wraps it (FuelPriceEntry.data) — one source of truth for the face
- WidgetMockScreen (-widgets launch arg): app icon + small + medium widget previews
  for App Store captures; AppIconPreview image set (1024 drip master)
- AppStoreScreenshots: 5-8 dark-mode tab captures with real Halifax data, 9 widgets
- 95/95 tests green; Release IPA rebuilt + re-served

FuelBoard/ContentView.swift

@@ -33,6 +33,7 @@ struct ContentView: View {
     @State private var isLoading = false
     @State private var statusMessage = ""
     @State private var showOnboarding = false
+    @State private var showWidgetMock = false
     @State private var selectedTab = 0
     @State private var locationManager = LocationManager()
     @StateObject private var monitor = ProximityMonitor()
@@ -172,6 +173,9 @@ struct ContentView: View {
                 showOnboarding = false
             }
         }
+        .fullScreenCover(isPresented: $showWidgetMock) {
+            WidgetMockScreen()
+        }
         .sheet(item: $monitor.pendingStationMap) { request in
             StationMapView(request: request)
         }
@@ -181,6 +185,7 @@ struct ContentView: View {
             // opens the given tab; `-skipOnboarding` skips onboarding
             // without touching the stored flag.
             let args = ProcessInfo.processInfo.arguments
+            showWidgetMock = args.contains("-widgets")
             if let i = args.firstIndex(of: "-tab"), i + 1 < args.count {
                 switch args[i + 1] {
                 case "favourites": selectedTab = 1