refactor(ui): Icon-Faerbung zentral im ICON-PAINTING-Block

Inline Foreground/Stroke an Icons entfernt — ein lokaler Wert schlaegt jeden
Style, dadurch erreichten Hover/Checked/Disabled das Icon nicht. Farbe wird
jetzt per Klasse gewaehlt (.danger, .star-btn.on, .active), alle Zustaende
liegen in einem geordneten Block in IslandStyles.axaml.

- Path.plan-icon -> Path.icon-stroke (gilt jetzt fuer Button und ToggleButton)
- Icon.Activity als gefuellte Kontur (PathIcon fuellt, Stroke-Polyline gab Blobs)
- BloodBrightBrush als Hover-Ton fuer destruktive Icons
- icon-btn:disabled bleibt transparent statt Fluent-Grau

src/ClaudeDo.Ui/Views/Islands/ListsIslandView.axaml

@@ -71,9 +71,7 @@
         <Button Grid.Column="2" Classes="icon-btn" VerticalAlignment="Center"
                 Command="{Binding OpenSettingsCommand}"
                 ToolTip.Tip="{loc:Tr lists.settingsTip}">
-          <PathIcon Data="{StaticResource Icon.Settings}"
-                    Width="15" Height="15"
-                    Foreground="{DynamicResource TextMuteBrush}"/>
+          <PathIcon Data="{StaticResource Icon.Settings}" Width="15" Height="15"/>
         </Button>
       </Grid>
     </Border>
@@ -207,20 +205,16 @@
             <StackPanel Orientation="Horizontal" Spacing="6">
               <PathIcon Data="{StaticResource Icon.Plus}"
                         Width="13" Height="13"
-                        Foreground="{DynamicResource TextMuteBrush}"
                         VerticalAlignment="Center"/>
               <TextBlock Classes="body"
                          Text="{loc:Tr lists.newList}"
-                         Foreground="{DynamicResource TextMuteBrush}"
                          VerticalAlignment="Center"/>
             </StackPanel>
           </Button>
           <Button Grid.Column="1" Classes="icon-btn" Margin="6,0,0,0"
                   Command="{Binding OpenRepoImportCommand}"
                   ToolTip.Tip="{loc:Tr lists.addReposTip}">
-            <PathIcon Data="{StaticResource Icon.Folder}"
-                      Width="14" Height="14"
-                      Foreground="{DynamicResource TextMuteBrush}"/>
+            <PathIcon Data="{StaticResource Icon.Folder}" Width="14" Height="14"/>
           </Button>
         </Grid>