Update with recovered code from VM binaries (Jan 1)

Recovered from decompiled OpenMaui.Controls.Linux.dll:
- SkiaShell.cs: FlyoutHeader, FlyoutFooter, scroll support (918 -> 1325 lines)
- X11Window.cs: Cursor support (XCreateFontCursor, XDefineCursor)
- All handlers with dark mode support
- All services with latest implementations
- LinuxApplication with theme change handling

Interop/XClientMessageEvent.cs

@@ -0,0 +1,22 @@
+using System;
+
+namespace Microsoft.Maui.Platform.Linux.Interop;
+
+public struct XClientMessageEvent
+{
+	public int Type;
+
+	public ulong Serial;
+
+	public int SendEvent;
+
+	public IntPtr Display;
+
+	public IntPtr Window;
+
+	public IntPtr MessageType;
+
+	public int Format;
+
+	public ClientMessageData Data;
+}