Live Activity: cheapest-in-radius Lock Screen/Dynamic Island pill

- Shared FuelBoardLiveActivityAttributes/ContentState (app + widget targets)
- FuelBoardLiveActivity Widget: ActivityConfiguration rendered by the widget
  extension - Lock Screen banner + Dynamic Island (leading/trailing/bottom,
  compact, minimal), tap anywhere -> maps:// directions to the best station
- LiveActivityManager (app side): request/update/end; mirrors the app list's
  TOP badge (selected fuel + chosen distance radius, price-then-distance
  ties); local start-date tracking for the 8h cap (this SDK's Activity has no
  startDate) - auto-restarts at 7h59m; silent no-op when disabled/denied
- Wiring: 250m/60s location hook (incl. background significant-change
  wake-ups), refresh completion, fuel/radius/unit changes, toggle flip
- Settings toggle + FuelStore persistence (keychain-backed, app-group)
- App-Info.plist: NSSupportsLiveActivities

Config/App-Info.plist

@@ -39,6 +39,8 @@
 	<string>FuelBoard uses Always location to alert you when you approach the cheapest station nearby.</string>
 	<key>NSLocalNetworkUsageDescription</key>
 	<string>FuelBoard connects to the FuelBoard Relay on your local network to download the latest fuel prices.</string>
+	<key>NSSupportsLiveActivities</key>
+	<true/>
 	<key>UIBackgroundModes</key>
 	<array>
 		<string>location</string>