add filter by network for legs, add full export for traction

lib/components/pages/legs.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:mileograph_flutter/components/legs/leg_card.dart';
+import 'package:mileograph_flutter/components/widgets/multi_select_filter.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';
@@ -19,6 +20,9 @@ class _LegsPageState extends State<LegsPage> {
   bool _initialised = false;
   bool _unallocatedOnly = false;
   bool _showMoreFilters = false;
+  bool _loadingNetworks = false;
+  List<String> _availableNetworks = [];
+  List<String> _selectedNetworks = [];
 
   @override
   void didChangeDependencies() {
@@ -26,9 +30,21 @@ class _LegsPageState extends State<LegsPage> {
     if (!_initialised) {
       _initialised = true;
       _refreshLegs();
+      _loadNetworks();
     }
   }
 
+  Future<void> _loadNetworks() async {
+    setState(() => _loadingNetworks = true);
+    final data = context.read<DataService>();
+    await data.fetchStationNetworks();
+    if (!mounted) return;
+    setState(() {
+      _availableNetworks = data.stationNetworks;
+      _loadingNetworks = false;
+    });
+  }
+
   Future<void> _refreshLegs() async {
     final data = context.read<DataService>();
     await data.fetchLegs(
@@ -36,6 +52,7 @@ class _LegsPageState extends State<LegsPage> {
       dateRangeStart: _formatDate(_startDate),
       dateRangeEnd: _formatDate(_endDate),
       unallocatedOnly: _unallocatedOnly,
+      networkFilter: _selectedNetworks,
     );
   }
 
@@ -48,6 +65,7 @@ class _LegsPageState extends State<LegsPage> {
       offset: data.legs.length,
       append: true,
       unallocatedOnly: _unallocatedOnly,
+      networkFilter: _selectedNetworks,
     );
   }
 
@@ -90,6 +108,7 @@ class _LegsPageState extends State<LegsPage> {
       _sortDirection = 0;
       _unallocatedOnly = false;
       _showMoreFilters = false;
+      _selectedNetworks = [];
     });
     _refreshLegs();
   }
@@ -209,6 +228,16 @@ class _LegsPageState extends State<LegsPage> {
                         spacing: 12,
                         runSpacing: 12,
                         children: [
+                          MultiSelectFilter(
+                            label: 'Networks',
+                            options: _availableNetworks,
+                            selected: _selectedNetworks,
+                            onChanged: (vals) async {
+                              setState(() => _selectedNetworks = vals);
+                              await _refreshLegs();
+                            },
+                            onRefresh: _loadingNetworks ? null : _loadNetworks,
+                          ),
                           FilterChip(
                             avatar: const Icon(Icons.flash_off),
                             label: const Text('Unallocated only'),
@@ -218,6 +247,15 @@ class _LegsPageState extends State<LegsPage> {
                               await _refreshLegs();
                             },
                           ),
+                          if (_loadingNetworks)
+                            const Padding(
+                              padding: EdgeInsets.only(left: 8.0),
+                              child: SizedBox(
+                                height: 20,
+                                width: 20,
+                                child: CircularProgressIndicator(strokeWidth: 2),
+                              ),
+                            ),
                         ],
                       ),
                     ),