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>

Native/GLibNative.cs

@@ -0,0 +1,111 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.Maui.Platform.Linux.Native;
+
+public static class GLibNative
+{
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    public delegate bool GSourceFunc(IntPtr userData);
+
+    private const string Lib = "libglib-2.0.so.0";
+
+    private static readonly List<GSourceFunc> _callbacks = new List<GSourceFunc>();
+    private static readonly object _callbackLock = new object();
+
+    [DllImport("libglib-2.0.so.0", EntryPoint = "g_idle_add")]
+    private static extern uint g_idle_add_native(GSourceFunc function, IntPtr data);
+
+    [DllImport("libglib-2.0.so.0", EntryPoint = "g_timeout_add")]
+    private static extern uint g_timeout_add_native(uint interval, GSourceFunc function, IntPtr data);
+
+    [DllImport("libglib-2.0.so.0", EntryPoint = "g_source_remove")]
+    public static extern bool SourceRemove(uint sourceId);
+
+    [DllImport("libglib-2.0.so.0", EntryPoint = "g_get_monotonic_time")]
+    public static extern long GetMonotonicTime();
+
+    public static uint IdleAdd(Func<bool> callback)
+    {
+        GSourceFunc wrapper = null;
+        wrapper = delegate
+        {
+            bool flag = false;
+            try
+            {
+                flag = callback();
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine("[GLibNative] Error in idle callback: " + ex.Message);
+            }
+            if (!flag)
+            {
+                lock (_callbackLock)
+                {
+                    _callbacks.Remove(wrapper);
+                }
+            }
+            return flag;
+        };
+        lock (_callbackLock)
+        {
+            _callbacks.Add(wrapper);
+        }
+        return g_idle_add_native(wrapper, IntPtr.Zero);
+    }
+
+    public static uint TimeoutAdd(uint intervalMs, Func<bool> callback)
+    {
+        GSourceFunc wrapper = null;
+        wrapper = delegate
+        {
+            bool flag = false;
+            try
+            {
+                flag = callback();
+            }
+            catch (Exception ex)
+            {
+                Console.WriteLine("[GLibNative] Error in timeout callback: " + ex.Message);
+            }
+            if (!flag)
+            {
+                lock (_callbackLock)
+                {
+                    _callbacks.Remove(wrapper);
+                }
+            }
+            return flag;
+        };
+        lock (_callbackLock)
+        {
+            _callbacks.Add(wrapper);
+        }
+        return g_timeout_add_native(intervalMs, wrapper, IntPtr.Zero);
+    }
+
+    public static void ClearCallbacks()
+    {
+        lock (_callbackLock)
+        {
+            _callbacks.Clear();
+        }
+    }
+
+    public static uint g_idle_add(GSourceFunc func, IntPtr data)
+    {
+        return g_idle_add_native(func, data);
+    }
+
+    public static uint g_timeout_add(uint intervalMs, GSourceFunc func, IntPtr data)
+    {
+        return g_timeout_add_native(intervalMs, func, data);
+    }
+
+    public static bool g_source_remove(uint tag)
+    {
+        return SourceRemove(tag);
+    }
+}