Migrate remaining legacy operator workflows

App.xaml.cs

@@ -1,3 +1,5 @@
+using Microsoft.Windows.AppLifecycle;
+
 namespace MBN_STOCK_WEBVIEW;
 
 /// <summary>
@@ -5,16 +7,53 @@ namespace MBN_STOCK_WEBVIEW;
 /// </summary>
 public partial class App : Application
 {
+    private const string MainInstanceKey = "Wickedness.MBNStockWebView.Main";
+
     private Window? _window;
+    private AppInstance? _mainInstance;
 
     public App()
     {
         InitializeComponent();
     }
 
-    protected override void OnLaunched(LaunchActivatedEventArgs args)
+    protected override async void OnLaunched(LaunchActivatedEventArgs args)
     {
+        var registeredInstance = AppInstance.FindOrRegisterForKey(MainInstanceKey);
+        if (!registeredInstance.IsCurrent)
+        {
+            try
+            {
+                var activation = AppInstance.GetCurrent().GetActivatedEventArgs();
+                if (activation is not null)
+                {
+                    await registeredInstance.RedirectActivationToAsync(activation);
+                }
+            }
+            finally
+            {
+                // The secondary process owns no DB, WebView, or playout runtime. End it only
+                // after the activation has been handed to the registered primary instance.
+                Exit();
+            }
+
+            return;
+        }
+
+        _mainInstance = registeredInstance;
+        _mainInstance.Activated += OnMainInstanceActivated;
         _window = new MainWindow();
         _window.Activate();
     }
+
+    private void OnMainInstanceActivated(object? sender, AppActivationArguments args)
+    {
+        var window = _window;
+        if (window is null)
+        {
+            return;
+        }
+
+        window.DispatcherQueue.TryEnqueue(window.Activate);
+    }
 }