Add ability to select distance unit

lib/components/pages/traction/traction.dart

@@ -6,6 +6,7 @@ import 'package:go_router/go_router.dart';
 import 'package:mileograph_flutter/components/traction/traction_card.dart';
 import 'package:mileograph_flutter/objects/objects.dart';
 import 'package:mileograph_flutter/services/data_service.dart';
+import 'package:mileograph_flutter/services/distance_unit_service.dart';
 import 'package:provider/provider.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 

lib/components/pages/traction/traction_page.dart

@@ -639,6 +639,7 @@ class _TractionPageState extends State<TractionPage> {
 
   Widget _buildClassStatsCard(BuildContext context) {
     final scheme = Theme.of(context).colorScheme;
+    final distanceUnits = context.watch<DistanceUnitService>();
     if (_classStatsLoading) {
       return Card(
         child: Padding(
@@ -721,9 +722,27 @@ class _TractionPageState extends State<TractionPage> {
               children: [
                 _metricTile('Had', hadCount),
                 _metricTile('Entries', entriesWithClass),
-                _metricTile('Avg mi / loco had', avgMileagePerLoco.toStringAsFixed(2)),
-                _metricTile('Avg mi / entry', avgMileagePerEntry.toStringAsFixed(2)),
-                _metricTile('Total mileage', totalMileage.toStringAsFixed(2)),
+                _metricTile(
+                  'Avg distance / loco had',
+                  distanceUnits.format(
+                    avgMileagePerLoco,
+                    decimals: 2,
+                  ),
+                ),
+                _metricTile(
+                  'Avg distance / entry',
+                  distanceUnits.format(
+                    avgMileagePerEntry,
+                    decimals: 2,
+                  ),
+                ),
+                _metricTile(
+                  'Total distance',
+                  distanceUnits.format(
+                    totalMileage,
+                    decimals: 2,
+                  ),
+                ),
               ],
             ),
             const SizedBox(height: 12),