feat(lists): assign a colour to a sidebar folder

Tints the folder name and its guide line; picked from a swatch row in the folder settings.

src/ClaudeDo.Ui/ViewModels/Islands/ListsIslandViewModel.cs

@@ -352,6 +352,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
                     Id = f.Id,
                     Name = f.Name,
                     IconKey = f.Icon ?? ListFolderIcon,
+                    Color = f.Color,
                     IsCollapsed = f.IsCollapsed,
                     ParentFolderId = f.ParentFolderId,
                 };
@@ -758,7 +759,7 @@ public sealed partial class ListsIslandViewModel : ViewModelBase, IDisposable
         if (folder is null || Dialogs is null || _services is null) return;
         var vm = _services.GetRequiredService<ListSettingsModalViewModel>();
         vm.ErrorReported += msg => ErrorReported?.Invoke(msg);
-        vm.BeginLoadFolder(folder.Id, folder.Name, folder.IconKey);
+        vm.BeginLoadFolder(folder.Id, folder.Name, folder.IconKey, folder.Color);
         await Dialogs.ShowListSettingsAsync(vm);
         // Rename, re-icon and delete all change the folder header (and delete releases its lists
         // back to the top level) — one reload covers every outcome.