Major production merge: GTK support, context menus, and dispatcher fixes

Core Infrastructure:
- Add Dispatching folder with LinuxDispatcher, LinuxDispatcherProvider, LinuxDispatcherTimer
- Add Native folder with P/Invoke wrappers (GTK, GLib, GDK, Cairo, WebKit)
- Add GTK host window system with GtkHostWindow and GtkSkiaSurfaceWidget
- Update LinuxApplication with GTK mode, theme handling, and icon support
- Fix duplicate LinuxDispatcher in LinuxMauiContext

Handlers:
- Add GtkWebViewManager and GtkWebViewPlatformView for GTK WebView
- Add FlexLayoutHandler and GestureManager
- Update multiple handlers with ToViewHandler fix and missing mappers
- Add MauiHandlerExtensions with ToViewHandler extension method

Views:
- Add SkiaContextMenu with hover, keyboard, and dark theme support
- Add LinuxDialogService with context menu management
- Add SkiaFlexLayout for flex container support
- Update SkiaShell with RefreshTheme, MauiShell, ContentRenderer
- Update SkiaWebView with SetMainWindow, ProcessGtkEvents
- Update SkiaImage with LoadFromBitmap method

Services:
- Add AppInfoService, ConnectivityService, DeviceDisplayService, DeviceInfoService
- Add GtkHostService, GtkContextMenuService, MauiIconGenerator

Window:
- Add CursorType enum and GtkHostWindow
- Update X11Window with SetIcon, SetCursor methods

Build: SUCCESS (0 errors)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Views/LinuxDialogService.cs

@@ -0,0 +1,101 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using SkiaSharp;
+
+namespace Microsoft.Maui.Platform;
+
+public static class LinuxDialogService
+{
+    private static readonly List<SkiaAlertDialog> _activeDialogs = new List<SkiaAlertDialog>();
+
+    private static Action? _invalidateCallback;
+
+    private static SkiaContextMenu? _activeContextMenu;
+
+    private static Action? _showPopupCallback;
+
+    private static Action? _hidePopupCallback;
+
+    public static bool HasActiveDialog => _activeDialogs.Count > 0;
+
+    public static SkiaAlertDialog? TopDialog
+    {
+        get
+        {
+            if (_activeDialogs.Count <= 0)
+            {
+                return null;
+            }
+            return _activeDialogs[_activeDialogs.Count - 1];
+        }
+    }
+
+    public static SkiaContextMenu? ActiveContextMenu => _activeContextMenu;
+
+    public static bool HasContextMenu => _activeContextMenu != null;
+
+    public static void SetInvalidateCallback(Action callback)
+    {
+        _invalidateCallback = callback;
+    }
+
+    public static Task<bool> ShowAlertAsync(string title, string message, string? accept, string? cancel)
+    {
+        var dialog = new SkiaAlertDialog(title, message, accept, cancel);
+        _activeDialogs.Add(dialog);
+        _invalidateCallback?.Invoke();
+        return dialog.Result;
+    }
+
+    internal static void HideDialog(SkiaAlertDialog dialog)
+    {
+        _activeDialogs.Remove(dialog);
+        _invalidateCallback?.Invoke();
+    }
+
+    public static void DrawDialogs(SKCanvas canvas, SKRect bounds)
+    {
+        DrawDialogsOnly(canvas, bounds);
+        DrawContextMenuOnly(canvas, bounds);
+    }
+
+    public static void DrawDialogsOnly(SKCanvas canvas, SKRect bounds)
+    {
+        foreach (var dialog in _activeDialogs)
+        {
+            dialog.Measure(new SKSize(bounds.Width, bounds.Height));
+            dialog.Arrange(bounds);
+            dialog.Draw(canvas);
+        }
+    }
+
+    public static void DrawContextMenuOnly(SKCanvas canvas, SKRect bounds)
+    {
+        if (_activeContextMenu != null)
+        {
+            _activeContextMenu.Draw(canvas);
+        }
+    }
+
+    public static void SetPopupCallbacks(Action showPopup, Action hidePopup)
+    {
+        _showPopupCallback = showPopup;
+        _hidePopupCallback = hidePopup;
+    }
+
+    public static void ShowContextMenu(SkiaContextMenu menu)
+    {
+        Console.WriteLine("[LinuxDialogService] ShowContextMenu called");
+        _activeContextMenu = menu;
+        _showPopupCallback?.Invoke();
+        _invalidateCallback?.Invoke();
+    }
+
+    public static void HideContextMenu()
+    {
+        _activeContextMenu = null;
+        _hidePopupCallback?.Invoke();
+        _invalidateCallback?.Invoke();
+    }
+}