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.Ui/Views/MainWindow.axaml

@@ -8,6 +8,7 @@
         x:Class="ClaudeDo.Ui.Views.MainWindow"
         x:DataType="vm:MainWindowViewModel"
         Title="ClaudeDo"
+        Icon="avares://ClaudeDo.App/Assets/ClaudeTask.ico"
         MinWidth="800" MinHeight="500"
         KeyDown="OnGlobalKeyDown">