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/Views/Modals/ListSettingsModalView.axaml

@@ -3,6 +3,7 @@
         xmlns:vm="clr-namespace:ClaudeDo.Ui.ViewModels.Modals"
         xmlns:ctl="using:ClaudeDo.Ui.Views.Controls"
         xmlns:loc="using:ClaudeDo.Ui.Localization"
+        xmlns:conv="using:ClaudeDo.Ui.Converters"
         x:Class="ClaudeDo.Ui.Views.Modals.ListSettingsModalView"
         x:DataType="vm:ListSettingsModalViewModel"
         Title="{loc:Tr modals.listSettings.title}"
@@ -88,6 +89,30 @@
                 <TextBox Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
               </StackPanel>
 
+              <StackPanel Spacing="4" IsVisible="{Binding IsFolder}">
+                <TextBlock Classes="field-label" Text="{loc:Tr modals.listSettings.folderColor}"/>
+                <ListBox ItemsSource="{x:Static vm:ListSettingsModalViewModel.FolderColorOptions}"
+                         SelectedItem="{Binding FolderColor, Mode=TwoWay}"
+                         Background="Transparent" BorderThickness="0"
+                         HorizontalAlignment="Left">
+                  <ListBox.ItemsPanel>
+                    <ItemsPanelTemplate>
+                      <WrapPanel/>
+                    </ItemsPanelTemplate>
+                  </ListBox.ItemsPanel>
+                  <ListBox.ItemTemplate>
+                    <DataTemplate x:DataType="x:String">
+                      <!-- "" renders as an empty ring: the "no colour" swatch. -->
+                      <Border Width="18" Height="18" Margin="3" CornerRadius="9"
+                              BorderThickness="1" BorderBrush="{DynamicResource LineBrightBrush}"
+                              Background="{Binding Converter={x:Static conv:HexBrushConverter.Instance}, ConverterParameter=Surface2Brush}"/>
+                    </DataTemplate>
+                  </ListBox.ItemTemplate>
+                </ListBox>
+                <TextBlock Text="{loc:Tr modals.listSettings.folderColorHint}"
+                           Opacity="0.6" FontSize="12" TextWrapping="Wrap"/>
+              </StackPanel>
+
               <StackPanel Spacing="4" IsVisible="{Binding !IsFolder}">
                 <TextBlock Classes="field-label" Text="{loc:Tr modals.listSettings.workingDirectory}"/>
                 <Grid ColumnDefinitions="*,Auto">