Add full XAML support for .NET MAUI compatibility

New features:
- MauiAppBuilderExtensions.UseOpenMauiLinux() for standard MAUI integration
- New template: openmaui-linux-xaml with full XAML support
- Standard MAUI XAML syntax (ContentPage, VerticalStackLayout, etc.)
- Resource dictionaries (Colors.xaml, Styles.xaml)
- Compiled XAML support via MauiXaml items

Templates now available:
- dotnet new openmaui-linux      (code-based UI)
- dotnet new openmaui-linux-xaml (XAML-based UI)

Usage:
    var builder = MauiApp.CreateBuilder();
    builder
        .UseMauiApp<App>()
        .UseOpenMauiLinux();  // Enable Linux with XAML

Hosting/MauiAppBuilderExtensions.cs

@@ -0,0 +1,193 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// Copyright (c) 2025 MarketAlly LLC
+
+using Microsoft.Maui;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Hosting;
+using Microsoft.Maui.Hosting;
+using OpenMaui.Platform.Linux.Handlers;
+
+namespace OpenMaui.Platform.Linux.Hosting;
+
+/// <summary>
+/// Extension methods for configuring OpenMaui Linux platform in a MAUI application.
+/// This enables full XAML support by registering Linux-specific handlers.
+/// </summary>
+public static class MauiAppBuilderExtensions
+{
+    /// <summary>
+    /// Configures the application to use OpenMaui Linux platform with full XAML support.
+    /// </summary>
+    /// <param name="builder">The MAUI app builder.</param>
+    /// <returns>The configured MAUI app builder.</returns>
+    /// <example>
+    /// <code>
+    /// var builder = MauiApp.CreateBuilder();
+    /// builder
+    ///     .UseMauiApp&lt;App&gt;()
+    ///     .UseOpenMauiLinux();  // Enable Linux support with XAML
+    /// </code>
+    /// </example>
+    public static MauiAppBuilder UseOpenMauiLinux(this MauiAppBuilder builder)
+    {
+        builder.ConfigureMauiHandlers(handlers =>
+        {
+            // Register all Linux platform handlers
+            // These map MAUI virtual views to our Skia platform views
+
+            // Basic Controls
+            handlers.AddHandler<Button, ButtonHandler>();
+            handlers.AddHandler<Label, LabelHandler>();
+            handlers.AddHandler<Entry, EntryHandler>();
+            handlers.AddHandler<Editor, EditorHandler>();
+            handlers.AddHandler<CheckBox, CheckBoxHandler>();
+            handlers.AddHandler<Switch, SwitchHandler>();
+            handlers.AddHandler<RadioButton, RadioButtonHandler>();
+
+            // Selection Controls
+            handlers.AddHandler<Slider, SliderHandler>();
+            handlers.AddHandler<Stepper, StepperHandler>();
+            handlers.AddHandler<Picker, PickerHandler>();
+            handlers.AddHandler<DatePicker, DatePickerHandler>();
+            handlers.AddHandler<TimePicker, TimePickerHandler>();
+
+            // Display Controls
+            handlers.AddHandler<Image, ImageHandler>();
+            handlers.AddHandler<ImageButton, ImageButtonHandler>();
+            handlers.AddHandler<ActivityIndicator, ActivityIndicatorHandler>();
+            handlers.AddHandler<ProgressBar, ProgressBarHandler>();
+
+            // Layout Controls
+            handlers.AddHandler<ScrollView, ScrollViewHandler>();
+            handlers.AddHandler<Border, BorderHandler>();
+            handlers.AddHandler<ContentView, ContentViewHandler>();
+            handlers.AddHandler<Frame, FrameHandler>();
+
+            // Collection Controls
+            handlers.AddHandler<CollectionView, CollectionViewHandler>();
+            handlers.AddHandler<CarouselView, CarouselViewHandler>();
+            handlers.AddHandler<IndicatorView, IndicatorViewHandler>();
+            handlers.AddHandler<RefreshView, RefreshViewHandler>();
+            handlers.AddHandler<SwipeView, SwipeViewHandler>();
+
+            // Navigation Controls
+            handlers.AddHandler<NavigationPage, NavigationPageHandler>();
+            handlers.AddHandler<TabbedPage, TabbedPageHandler>();
+            handlers.AddHandler<FlyoutPage, FlyoutPageHandler>();
+            handlers.AddHandler<Shell, ShellHandler>();
+
+            // Page Controls
+            handlers.AddHandler<Page, PageHandler>();
+            handlers.AddHandler<ContentPage, PageHandler>();
+
+            // Graphics
+            handlers.AddHandler<GraphicsView, GraphicsViewHandler>();
+
+            // Search
+            handlers.AddHandler<SearchBar, SearchBarHandler>();
+
+            // Window
+            handlers.AddHandler<Window, WindowHandler>();
+        });
+
+        // Register Linux-specific services
+        builder.Services.AddSingleton<ILinuxPlatformServices, LinuxPlatformServices>();
+
+        return builder;
+    }
+
+    /// <summary>
+    /// Configures the application to use OpenMaui Linux with custom handler configuration.
+    /// </summary>
+    /// <param name="builder">The MAUI app builder.</param>
+    /// <param name="configureHandlers">Action to configure additional handlers.</param>
+    /// <returns>The configured MAUI app builder.</returns>
+    public static MauiAppBuilder UseOpenMauiLinux(
+        this MauiAppBuilder builder,
+        Action<IMauiHandlersCollection>? configureHandlers)
+    {
+        builder.UseOpenMauiLinux();
+
+        if (configureHandlers != null)
+        {
+            builder.ConfigureMauiHandlers(configureHandlers);
+        }
+
+        return builder;
+    }
+}
+
+/// <summary>
+/// Interface for Linux platform services.
+/// </summary>
+public interface ILinuxPlatformServices
+{
+    /// <summary>
+    /// Gets the display server type (X11 or Wayland).
+    /// </summary>
+    DisplayServerType DisplayServer { get; }
+
+    /// <summary>
+    /// Gets the current DPI scale factor.
+    /// </summary>
+    float ScaleFactor { get; }
+
+    /// <summary>
+    /// Gets whether high contrast mode is enabled.
+    /// </summary>
+    bool IsHighContrastEnabled { get; }
+}
+
+/// <summary>
+/// Display server types supported by OpenMaui.
+/// </summary>
+public enum DisplayServerType
+{
+    /// <summary>X11 display server.</summary>
+    X11,
+    /// <summary>Wayland display server.</summary>
+    Wayland,
+    /// <summary>Auto-detected display server.</summary>
+    Auto
+}
+
+/// <summary>
+/// Implementation of Linux platform services.
+/// </summary>
+internal class LinuxPlatformServices : ILinuxPlatformServices
+{
+    public DisplayServerType DisplayServer => DetectDisplayServer();
+    public float ScaleFactor => DetectScaleFactor();
+    public bool IsHighContrastEnabled => DetectHighContrast();
+
+    private static DisplayServerType DetectDisplayServer()
+    {
+        var waylandDisplay = Environment.GetEnvironmentVariable("WAYLAND_DISPLAY");
+        if (!string.IsNullOrEmpty(waylandDisplay))
+            return DisplayServerType.Wayland;
+
+        var display = Environment.GetEnvironmentVariable("DISPLAY");
+        if (!string.IsNullOrEmpty(display))
+            return DisplayServerType.X11;
+
+        return DisplayServerType.Auto;
+    }
+
+    private static float DetectScaleFactor()
+    {
+        // Try GDK_SCALE first
+        var gdkScale = Environment.GetEnvironmentVariable("GDK_SCALE");
+        if (float.TryParse(gdkScale, out var scale))
+            return scale;
+
+        // Default to 1.0
+        return 1.0f;
+    }
+
+    private static bool DetectHighContrast()
+    {
+        var highContrast = Environment.GetEnvironmentVariable("GTK_THEME");
+        return highContrast?.Contains("HighContrast", StringComparison.OrdinalIgnoreCase) ?? false;
+    }
+}