feat(installer): add WPF installer/configurator project

Standalone WPF app (ClaudeDo.Installer) that handles full installation
and ongoing configuration of ClaudeDo. Two modes: wizard for first run,
tabbed settings panel for subsequent launches. Page-based extensibility
via IInstallerPage interface — adding new config sections requires only
one new class.

Install pipeline: dotnet publish, deploy binaries, write configs, init
DB (via SchemaInitializer from ClaudeDo.Data), register Windows Service,
create shortcuts. Dark theme matching the Avalonia app (forest teal accent).

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

src/ClaudeDo.Installer/Core/StepIndicatorConverter.cs

@@ -0,0 +1,37 @@
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+using System.Windows.Media;
+
+namespace ClaudeDo.Installer.Core;
+
+/// <summary>
+/// Multi-value converter: compares the page's index with the current page index
+/// to determine step indicator styling.
+/// </summary>
+public sealed class StepActiveConverter : IMultiValueConverter
+{
+    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
+    {
+        if (values.Length < 2 ||
+            values[0] is not IInstallerPage page ||
+            values[1] is not IInstallerPage currentPage)
+            return DependencyProperty.UnsetValue;
+
+        var isActive = ReferenceEquals(page, currentPage);
+
+        var key = parameter?.ToString() switch
+        {
+            "Background" => isActive ? "AccentBrush" : "WindowBgBrush",
+            "Foreground" => isActive ? "TextPrimaryBrush" : "TextMutedBrush",
+            "BorderBrush" => isActive ? "AccentBrush" : "BorderSubtleBrush",
+            _ => null
+        };
+
+        if (key is null) return DependencyProperty.UnsetValue;
+        return Application.Current.Resources[key] as SolidColorBrush ?? DependencyProperty.UnsetValue;
+    }
+
+    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}