Add ability to select distance unit

lib/components/legs/leg_card.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:go_router/go_router.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';
 
 class LegCard extends StatefulWidget {
@@ -26,6 +27,7 @@ class _LegCardState extends State<LegCard> {
   @override
   Widget build(BuildContext context) {
     final leg = widget.leg;
+    final distanceUnits = context.watch<DistanceUnitService>();
     final routeSegments = _parseRouteSegments(leg.route);
     final textTheme = Theme.of(context).textTheme;
     return Card(
@@ -181,7 +183,7 @@ class _LegCardState extends State<LegCard> {
               crossAxisAlignment: CrossAxisAlignment.end,
               children: [
                 Text(
-                  '${leg.mileage.toStringAsFixed(1)} mi',
+                  distanceUnits.format(leg.mileage, decimals: 1),
                   style: textTheme.labelLarge?.copyWith(
                     fontWeight: FontWeight.w700,
                   ),