Resolution dropdown, list-focus preservation, unified dark theme, startup logging, and memory map

- Bottom-bar resolution dropdown (1080p60/1080p30/720p60/480p30) with tooltip
  on finding upload bandwidth; disabled while live; no in-app speed test
- FocusPreservingListBox keeps selection/focus coherent when a selected
  scene/source is deleted (skip hidden scenes; leave list when empty)
- Themes/Controls.xaml: single dark-theme dictionary merged once in App.xaml;
  custom ComboBox template fixes SelectionBoxItem rendering; GoLiveWindow and
  ReuseImageDialog consolidated onto shared styles
- AppLog file logger + AppDomain/Dispatcher exception hooks; checkpointed
  MainWindow/VM/dialog constructors (caught MenuItemRole.Separator XAML crash)
- Memory map: schema.md conventions, per-directory index.md, updated ai.md/
  TASKS.md/README.md (OAuth creds real; token persistence still pending)

App.xaml.cs

@@ -1,13 +1,34 @@
-using System.Configuration;
-using System.Data;
-using System.Windows;
-
-namespace ytLive;
-
-/// <summary>
-/// Interaction logic for App.xaml
-/// </summary>
-public partial class App : Application
-{
-}
-
+using System.Windows;
+using System.Windows.Threading;
+using ytLive.Helpers;
+
+namespace ytLive;
+
+/// <summary>
+/// Interaction logic for App.xaml
+/// </summary>
+public partial class App : Application
+{
+    public App()
+    {
+        AppLog.Write("App ctor");
+    }
+
+    protected override void OnStartup(StartupEventArgs e)
+    {
+        // The app is a WinExe (no visible console) and is often debugged from
+        // WSL where it can't even run, so startup checkpoints and any unhandled
+        // exception are written to %APPDATA%\ytLlive\startup.log via AppLog.
+        AppDomain.CurrentDomain.UnhandledException += (_, args) =>
+            AppLog.Write(args.ExceptionObject is Exception ex
+                ? "AppDomain unhandled exception: " + ex
+                : "AppDomain unhandled exception object: " + args.ExceptionObject);
+
+        DispatcherUnhandledException += (_, args) =>
+            AppLog.Write(args.Exception, "Dispatcher unhandled exception");
+
+        AppLog.Write("App OnStartup begin");
+        base.OnStartup(e);
+        AppLog.Write("App OnStartup end");
+    }
+}