Add accent colour picker, fix empty user card when accepting friend request, add button to transfer allocations

lib/components/pages/traction/traction_page.dart

@@ -12,6 +12,7 @@ class TractionPage extends StatefulWidget {
     this.selectionMode = false,
     this.selectionSingle = false,
     this.replacementPendingLocoId,
+    this.transferFromLocoId,
     this.onSelect,
     this.selectedKeys = const {},
   });
@@ -19,6 +20,7 @@ class TractionPage extends StatefulWidget {
   final bool selectionMode;
   final bool selectionSingle;
   final int? replacementPendingLocoId;
+  final int? transferFromLocoId;
   final ValueChanged<LocoSummary>? onSelect;
   final Set<String> selectedKeys;
 
@@ -33,6 +35,7 @@ class _TractionPageState extends State<TractionPage> {
   final _nameController = TextEditingController();
   bool _mileageFirst = true;
   bool _initialised = false;
+  int? get _transferFromLocoId => widget.transferFromLocoId;
   bool _showAdvancedFilters = false;
   String? _selectedClass;
   late Set<String> _selectedKeys;
@@ -1200,6 +1203,53 @@ class _TractionPageState extends State<TractionPage> {
     }
   }
 
+  Future<void> _confirmTransfer(LocoSummary target) async {
+    final fromId = _transferFromLocoId;
+    if (fromId == null) return;
+    final navContext = context;
+    final messenger = ScaffoldMessenger.of(navContext);
+    final confirmed = await showDialog<bool>(
+      context: navContext,
+      builder: (dialogContext) {
+        return AlertDialog(
+          title: const Text('Transfer allocations?'),
+          content: Text(
+            'Transfer all allocations from this loco to ${target.locoClass} ${target.number}?',
+          ),
+          actions: [
+            TextButton(
+              onPressed: () => Navigator.of(dialogContext).pop(false),
+              child: const Text('Cancel'),
+            ),
+            FilledButton(
+              onPressed: () => Navigator.of(dialogContext).pop(true),
+              child: const Text('Transfer'),
+            ),
+          ],
+        );
+      },
+    );
+    if (confirmed != true) return;
+    if (!navContext.mounted) return;
+    try {
+      final data = navContext.read<DataService>();
+      await data.transferAllocations(fromLocoId: fromId, toLocoId: target.id);
+      if (navContext.mounted) {
+        messenger.showSnackBar(
+          const SnackBar(content: Text('Allocations transferred')),
+        );
+      }
+      await _refreshTraction(preservePosition: true);
+      if (navContext.mounted) navContext.pop();
+    } catch (e) {
+      if (navContext.mounted) {
+        messenger.showSnackBar(
+          SnackBar(content: Text('Failed to transfer allocations: $e')),
+        );
+      }
+    }
+  }
+
   bool _isSelected(LocoSummary loco) {
     final keyVal = '${loco.locoClass}-${loco.number}';
     return _selectedKeys.contains(keyVal);
@@ -1348,12 +1398,18 @@ class _TractionPageState extends State<TractionPage> {
                         widget.replacementPendingLocoId == null
                     ? () => _toggleSelection(loco)
                     : null,
-              onReplacePending: widget.selectionMode &&
-                      widget.selectionSingle &&
-                      widget.replacementPendingLocoId != null
-                  ? () => _confirmReplacePending(loco)
-                  : null,
-            );
+                onReplacePending: widget.selectionMode &&
+                        widget.selectionSingle &&
+                        widget.replacementPendingLocoId != null
+                    ? () => _confirmReplacePending(loco)
+                    : null,
+                onTransferAllocations: widget.selectionMode &&
+                        widget.selectionSingle &&
+                        widget.transferFromLocoId != null &&
+                        widget.transferFromLocoId != loco.id
+                    ? () => _confirmTransfer(loco)
+                    : null,
+              );
           }
 
           return Padding(