Raise deployment target to iOS 26.0; enable CarPlay Live Activity

- IPHONEOS_DEPLOYMENT_TARGET 17.0 -> 26.0 (iPhone 11+, Apple's current floor)
- Widget CarPlay disfavor is now unconditional (no #available guard)
- Live Activity gains supplementalActivityFamilies([.small]) so it renders
  in the car's small slot on CarPlay Ultra (display-only: FuelBoard has no
  CarPlay entitlement, car taps can't launch anything)

FuelBoardWidgets/FuelBoardLiveActivityView.swift

@@ -10,7 +10,10 @@ import WidgetKit
 
 /// The Live Activity itself — registered in the widget bundle alongside the
 /// regular price widget. No CarPlay entitlement involved: this renders on the
-/// Lock Screen, Dynamic Island, and (iOS 26+ / CarPlay Ultra) the car display.
+/// Lock Screen, Dynamic Island, and the car display (CarPlay Ultra, iOS 26+).
+/// `.supplementalActivityFamilies([.small])` makes it eligible for the car's
+/// small Live Activity slot — display-only there (FuelBoard is not a
+/// CarPlay-enabled app, so car-side taps can't launch anything).
 struct FuelBoardLiveActivity: Widget {
     var body: some WidgetConfiguration {
         ActivityConfiguration(for: FuelBoardLiveActivityAttributes.self) { context in
@@ -37,6 +40,7 @@ struct FuelBoardLiveActivity: Widget {
                     .font(.caption2.bold().monospacedDigit())
             }
         }
+        .supplementalActivityFamilies([.small])
     }
 }