fix: add SettingsProvider to SpeedometerViewModel and fix ProviderNotFoundException

- SpeedometerViewModel now requires both LocationRepository and SettingsProvider
- SpeedometerView uses SettingsProvider.currentTheme instead of non-existent Theme provider
- main.dart: SettingsProvider created before SpeedometerViewModel in provider hierarchy
- Restores proper DI wiring after layered architecture refactor

lib/ui/features/speedometer/speedometer_view_model.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/widgets.dart';
-import 'package:provider/provider.dart';
 import '../../../core/constants/speed_unit.dart';
 import '../../../data/models/location_data.dart';
 import '../../../data/repositories/location_repository.dart';
@@ -11,22 +10,16 @@ import '../../../providers/settings_provider.dart';
 /// the current display state to the view. No data-layer logic here.
 class SpeedometerViewModel extends ChangeNotifier {
   final LocationRepository _repository;
-  SettingsProvider? _settings;
+  final SettingsProvider _settings;
 
-  SpeedUnit get displayUnit => _settings?.currentUnit ?? SpeedUnit.kmh;
+  SpeedUnit get displayUnit => _settings.currentUnit;
   LocationData get displayData => _repository.currentData;
   String get displaySpeedText => _repository.currentData.displaySpeed;
   String get displayHeading => _repository.currentData.displayHeading;
   bool get isSpeedValid => _repository.currentData.isSpeedValid;
   bool get isHeadingValid => _repository.currentData.isHeadingValid;
 
-  SpeedometerViewModel(this._repository);
-
-  /// Call when the ViewModel is inserted into the provider tree so it
-  /// can listen to SettingsProvider and repository state.
-  void attach(BuildContext context) {
-    _settings = context.read<SettingsProvider>();
-  }
+  SpeedometerViewModel(this._repository, this._settings);
 
   double get displaySpeed {
     return displayUnit.convert(_repository.currentData.speed);