add transfer all button for admins

lib/components/pages/traction/traction_page.dart

@@ -15,6 +15,7 @@ class TractionPage extends StatefulWidget {
     this.replacementPendingLocoId,
     this.transferFromLabel,
     this.transferFromLocoId,
+    this.transferAllAllocations = false,
     this.onSelect,
     this.selectedKeys = const {},
   });
@@ -24,6 +25,7 @@ class TractionPage extends StatefulWidget {
   final int? replacementPendingLocoId;
   final String? transferFromLabel;
   final int? transferFromLocoId;
+  final bool transferAllAllocations;
   final ValueChanged<LocoSummary>? onSelect;
   final Set<String> selectedKeys;
 
@@ -39,6 +41,12 @@ class _TractionPageState extends State<TractionPage> {
   bool _mileageFirst = true;
   bool _initialised = false;
   int? get _transferFromLocoId => widget.transferFromLocoId;
+  bool get _transferAllAllocations {
+    if (widget.transferAllAllocations) return true;
+    final param =
+        GoRouterState.of(context).uri.queryParameters['transferAll'];
+    return param?.toLowerCase() == 'true' || param == '1';
+  }
   bool _showAdvancedFilters = false;
   String? _selectedClass;
   late Set<String> _selectedKeys;
@@ -1315,13 +1323,19 @@ class _TractionPageState extends State<TractionPage> {
       context: navContext,
       builder: (dialogContext) {
         return AlertDialog(
-          title: const Text('Transfer allocations?'),
+          title: Text(
+            _transferAllAllocations
+                ? 'Transfer all allocations?'
+                : 'Transfer allocations?',
+          ),
           content: Column(
             mainAxisSize: MainAxisSize.min,
             crossAxisAlignment: CrossAxisAlignment.start,
             children: [
               Text(
-                'Transfer all allocations from $fromLabel to $toLabel?',
+                _transferAllAllocations
+                    ? 'Transfer all user allocations from $fromLabel to $toLabel?'
+                    : 'Transfer all allocations from $fromLabel to $toLabel?',
               ),
               const SizedBox(height: 12),
               Text(
@@ -1351,10 +1365,23 @@ class _TractionPageState extends State<TractionPage> {
     if (!navContext.mounted) return;
     try {
       final data = navContext.read<DataService>();
-      await data.transferAllocations(fromLocoId: fromId, toLocoId: target.id);
+      if (_transferAllAllocations) {
+        await data.transferAllAllocations(
+          fromLocoId: fromId,
+          toLocoId: target.id,
+        );
+      } else {
+        await data.transferAllocations(fromLocoId: fromId, toLocoId: target.id);
+      }
       if (navContext.mounted) {
         messenger.showSnackBar(
-          const SnackBar(content: Text('Allocations transferred')),
+          SnackBar(
+            content: Text(
+              _transferAllAllocations
+                  ? 'All allocations transferred'
+                  : 'Allocations transferred',
+            ),
+          ),
         );
       }
       await _refreshTraction(preservePosition: true);
@@ -1426,7 +1453,9 @@ class _TractionPageState extends State<TractionPage> {
           const SizedBox(width: 8),
           Expanded(
             child: Text(
-              'Transferring allocations from $label. Select a loco to transfer to.',
+              _transferAllAllocations
+                  ? 'Transferring all allocations from $label. Select a loco to transfer to.'
+                  : 'Transferring allocations from $label. Select a loco to transfer to.',
               style: const TextStyle(fontWeight: FontWeight.w600),
             ),
           ),