Refactor application structure and add database support

Changed App.xaml.cs to implement dependency injection with Microsoft.Extensions.Hosting, initializing services for LandingWindow and LandingViewModel.

Removed MainWindow.xaml and MainWindow.xaml.cs, shifting to a new landing window structure.

Added Ghost.Database project with necessary database functionality and created ProjectRepository for project management.

Added ProjectInfo and TemplateInfo data models for project attributes.

Added CreateProjectViewModel and LandingViewModel for managing view models using Community Toolkit for MVVM.

Created new XAML pages for project creation, opening projects, and the landing window, along with their corresponding code-behind files.

Added AssemblyInfo.cs for internal visibility to facilitate testing.

Ghost.Editor/App.xaml.cs

@@ -1,4 +1,9 @@
-using Microsoft.UI.Xaml;
+using Ghost.Editor.View.Windows;
+using Ghost.Editor.ViewModel.Windows;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.UI.Xaml;
+using System;
 
 // To learn more about WinUI, the WinUI project structure,
 // and more about our project templates, see: http://aka.ms/winui-project-info.
@@ -10,6 +15,23 @@ namespace Ghost.Editor
     /// </summary>
     public partial class App : Application
     {
+        private Window? _window;
+
+        public IHost Host
+        {
+            get;
+        }
+
+        public static T GetService<T>() where T : class
+        {
+            if ((Current as App)!.Host.Services.GetService(typeof(T)) is not T service)
+            {
+                throw new ArgumentException($"{typeof(T)} needs to be registered in ConfigureServices within App.xaml.cs.");
+            }
+
+            return service;
+        }
+
         /// <summary>
         /// Initializes the singleton application object.  This is the first line of authored code
         /// executed, and as such is the logical equivalent of main() or WinMain().
@@ -17,6 +39,16 @@ namespace Ghost.Editor
         public App()
         {
             InitializeComponent();
+
+            Host = Microsoft.Extensions.Hosting.Host.
+                CreateDefaultBuilder().
+                UseContentRoot(AppContext.BaseDirectory).
+                ConfigureServices((context, services) =>
+                {
+                    services.AddTransient<LandingWindow>();
+                    services.AddTransient<LandingViewModel>();
+                })
+                .Build();
         }
 
         /// <summary>
@@ -25,10 +57,11 @@ namespace Ghost.Editor
         /// <param name="args">Details about the launch request and process.</param>
         protected override void OnLaunched(LaunchActivatedEventArgs args)
         {
-            m_window = new MainWindow();
-            m_window.Activate();
-        }
+            base.OnLaunched(args);
+            Host.Start();
 
-        private Window? m_window;
+            _window = GetService<LandingWindow>();
+            _window.Activate();
+        }
     }
-}
+}