feat: initial datamodel + ef connection and migrations

Initial version of the data model
Includes EF initialization and migrations
EF migrations are applied on application start

TournamentOrganizer.Browser/Program.cs

@@ -0,0 +1,15 @@
+using System.Runtime.Versioning;
+using System.Threading.Tasks;
+using Avalonia;
+using Avalonia.Browser;
+using TournamentOrganizer;
+
+internal sealed partial class Program
+{
+    private static Task Main(string[] args) => BuildAvaloniaApp()
+            .WithInterFont()
+            .StartBrowserAppAsync("out");
+
+    public static AppBuilder BuildAvaloniaApp()
+        => AppBuilder.Configure<App>();
+}