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>

Handlers/GtkWebViewManager.cs

@@ -0,0 +1,60 @@
+using System.Collections.Generic;
+using Microsoft.Maui.Platform.Linux.Window;
+
+namespace Microsoft.Maui.Platform.Linux.Handlers;
+
+/// <summary>
+/// Manages WebView instances within the GTK host window.
+/// Handles creation, layout updates, and cleanup of WebKit-based web views.
+/// </summary>
+public sealed class GtkWebViewManager
+{
+    private readonly GtkHostWindow _host;
+    private readonly Dictionary<object, GtkWebViewPlatformView> _webViews = new();
+
+    public GtkWebViewManager(GtkHostWindow host)
+    {
+        _host = host;
+    }
+
+    public GtkWebViewPlatformView CreateWebView(object key, int x, int y, int width, int height)
+    {
+        var webView = new GtkWebViewPlatformView();
+        _webViews[key] = webView;
+        _host.AddWebView(webView.Widget, x, y, width, height);
+        return webView;
+    }
+
+    public void UpdateLayout(object key, int x, int y, int width, int height)
+    {
+        if (_webViews.TryGetValue(key, out var webView))
+        {
+            _host.MoveResizeWebView(webView.Widget, x, y, width, height);
+        }
+    }
+
+    public GtkWebViewPlatformView? GetWebView(object key)
+    {
+        return _webViews.TryGetValue(key, out var webView) ? webView : null;
+    }
+
+    public void RemoveWebView(object key)
+    {
+        if (_webViews.TryGetValue(key, out var webView))
+        {
+            _host.RemoveWebView(webView.Widget);
+            webView.Dispose();
+            _webViews.Remove(key);
+        }
+    }
+
+    public void Clear()
+    {
+        foreach (var kvp in _webViews)
+        {
+            _host.RemoveWebView(kvp.Value.Widget);
+            kvp.Value.Dispose();
+        }
+        _webViews.Clear();
+    }
+}