unify pipeline, load friends leaderboard from homepage data

lib/services/data_service/data_service_core.dart

@@ -169,10 +169,12 @@ class DataService extends ChangeNotifier {
       _homepageStats = HomepageStats.fromJson(json);
       _trips = [...(_homepageStats?.trips ?? const [])]
         ..sort(TripSummary.compareByDateDesc);
+      _friendsLeaderboard = _homepageStats?.friendsLeaderboard ?? [];
     } catch (e) {
       debugPrint('Failed to fetch homepage stats: $e');
       _homepageStats = null;
       _trips = [];
+      _friendsLeaderboard = [];
     } finally {
       _isHomepageLoading = false;
       _notifyAsync();