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>

Services/GtkContextMenuService.cs

@@ -0,0 +1,90 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Microsoft.Maui.Platform.Linux.Native;
+
+namespace Microsoft.Maui.Platform.Linux.Services;
+
+/// <summary>
+/// Service for displaying native GTK context menus in MAUI applications.
+/// Provides popup menu functionality with action callbacks.
+/// </summary>
+public static class GtkContextMenuService
+{
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void ActivateCallback(IntPtr menuItem, IntPtr userData);
+
+    // Keep references to prevent garbage collection
+    private static readonly List<ActivateCallback> _callbacks = new();
+    private static readonly List<Action> _actions = new();
+
+    public static void ShowContextMenu(List<GtkMenuItem> items)
+    {
+        if (items == null || items.Count == 0)
+        {
+            return;
+        }
+
+        _callbacks.Clear();
+        _actions.Clear();
+
+        IntPtr menu = GtkNative.gtk_menu_new();
+        if (menu == IntPtr.Zero)
+        {
+            Console.WriteLine("[GtkContextMenuService] Failed to create GTK menu");
+            return;
+        }
+
+        foreach (var item in items)
+        {
+            IntPtr menuItem;
+
+            if (item.IsSeparator)
+            {
+                menuItem = GtkNative.gtk_separator_menu_item_new();
+            }
+            else
+            {
+                menuItem = GtkNative.gtk_menu_item_new_with_label(item.Text);
+                GtkNative.gtk_widget_set_sensitive(menuItem, item.IsEnabled);
+
+                if (item.IsEnabled && item.Action != null)
+                {
+                    var action = item.Action;
+                    _actions.Add(action);
+                    int actionIndex = _actions.Count - 1;
+
+                    ActivateCallback callback = delegate
+                    {
+                        Console.WriteLine("[GtkContextMenuService] Menu item activated: " + item.Text);
+                        _actions[actionIndex]?.Invoke();
+                    };
+                    _callbacks.Add(callback);
+
+                    GtkNative.g_signal_connect_data(
+                        menuItem,
+                        "activate",
+                        Marshal.GetFunctionPointerForDelegate(callback),
+                        IntPtr.Zero,
+                        IntPtr.Zero,
+                        0);
+                }
+            }
+
+            GtkNative.gtk_menu_shell_append(menu, menuItem);
+            GtkNative.gtk_widget_show(menuItem);
+        }
+
+        GtkNative.gtk_widget_show(menu);
+
+        IntPtr currentEvent = GtkNative.gtk_get_current_event();
+        GtkNative.gtk_menu_popup_at_pointer(menu, currentEvent);
+
+        if (currentEvent != IntPtr.Zero)
+        {
+            GtkNative.gdk_event_free(currentEvent);
+        }
+
+        Console.WriteLine($"[GtkContextMenuService] Showed GTK menu with {items.Count} items");
+    }
+}