feat(branding): add app and installer icons

- app: ClaudeTask.ico wired as ApplicationIcon and MainWindow.Icon
  via avares URI
- installer: ClaudeTaskSetup.ico wired as ApplicationIcon and embedded
  as a WPF Resource so WizardWindow and SettingsWindow can reference it
  via pack URI

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Installer/Views/SettingsWindow.xaml

@@ -3,6 +3,7 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:views="clr-namespace:ClaudeDo.Installer.Views"
         Title="ClaudeDo Settings"
+        Icon="/ClaudeTaskSetup.ico"
         Width="720" Height="520"
         MinWidth="620" MinHeight="460"
         WindowStartupLocation="CenterScreen"

src/ClaudeDo.Installer/Views/WizardWindow.xaml

@@ -3,6 +3,7 @@
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:views="clr-namespace:ClaudeDo.Installer.Views"
         Title="ClaudeDo Installer"
+        Icon="/ClaudeTaskSetup.ico"
         Width="720" Height="520"
         MinWidth="620" MinHeight="460"
         WindowStartupLocation="CenterScreen"