Initial samples: TodoApp and ShellDemo

Two sample applications demonstrating OpenMaui Linux:

TodoApp:
- Full task manager with NavigationPage
- CollectionView with XAML data binding
- DisplayAlert dialogs
- Grid layouts with star sizing

ShellDemo:
- Comprehensive control showcase
- Shell with flyout navigation
- All core MAUI controls demonstrated
- Real-time event logging

Both samples reference OpenMaui.Controls.Linux via NuGet.

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

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

TodoApp/App.cs

@@ -0,0 +1,21 @@
+// TodoApp - Main Application with NavigationPage
+
+using Microsoft.Maui.Controls;
+
+namespace TodoApp;
+
+public class App : Application
+{
+    public static NavigationPage? NavigationPage { get; private set; }
+
+    public App()
+    {
+        NavigationPage = new NavigationPage(new TodoListPage())
+        {
+            Title = "OpenMaui Todo App",
+            BarBackgroundColor = Color.FromArgb("#2196F3"),
+            BarTextColor = Colors.White
+        };
+        MainPage = NavigationPage;
+    }
+}