add loco legs panel

lib/services/data_service.dart

@@ -177,6 +177,38 @@ class DataService extends ChangeNotifier {
     );
   }
 
+  Future<List<Leg>> fetchLegsForLoco(
+    int locoId, {
+    bool includeNonPowering = false,
+  }) async {
+    if (locoId <= 0) return [];
+    final params =
+        includeNonPowering ? '?include_non_powering=true' : '';
+    try {
+      final json = await api.get('/legs/$locoId$params');
+      dynamic list = json;
+      if (json is Map) {
+        for (final key in ['legs', 'data', 'results']) {
+          if (json[key] is List) {
+            list = json[key];
+            break;
+          }
+        }
+      }
+      if (list is List) {
+        return list
+            .whereType<Map>()
+            .map((e) => Leg.fromJson(Map<String, dynamic>.from(e)))
+            .toList();
+      }
+      debugPrint('Unexpected loco legs response: $json');
+      return [];
+    } catch (e) {
+      debugPrint('Failed to fetch loco legs for $locoId: $e');
+      return [];
+    }
+  }
+
   Future<void> fetchHadTraction({int offset = 0, int limit = 100}) async {
     await fetchTraction(
       hadOnly: true,