Brand logo: one locked image layer per scene above the background, image from App Settings

- Source.IsBrandLogo persisted (additive migration); layer healed on load, removal blocked
- Image stored as an asset; settings keep the asset id and file name
- App Settings: Brand Logo file field with Browse
- Default placement top-left; per-scene eye uses the existing element visibility
Test: BrandLogoTests; layout/background tests pass (34). Not pushed.

ViewModels/MainViewModel.Background.cs

@@ -438,6 +438,7 @@ public partial class MainViewModel
                 StampDefaultBackgroundAsset(background, scene.Name);
         }
         SeedOnAirImage();
+        EnsureBrandLogos();
         OnPropertyChanged(nameof(ShowSourcesEmptyHint));
         OnPropertyChanged(nameof(LayerCount));
     }

ViewModels/MainViewModel.BrandLogo.cs

@@ -0,0 +1,77 @@
+using System.IO;
+using System.Windows.Input;
+using ytLive.Helpers;
+using ytLive.Models;
+
+namespace ytLive.ViewModels;
+
+/// <summary>
+/// The permanent brand logo: one image layer in every scene, directly above the background.
+/// Its image comes from App Settings; each scene keeps its own visibility (the eye toggle).
+/// </summary>
+public partial class MainViewModel
+{
+    internal const double BrandLogoX = 32;
+    internal const double BrandLogoY = 32;
+    internal const double BrandLogoWidth = 240;
+    internal const double BrandLogoHeight = 120;
+
+    private ICommand? _browseBrandLogo;
+
+    public ICommand BrowseBrandLogoCommand => _browseBrandLogo ??= new RelayCommand(_ => BrowseBrandLogo());
+
+    public string BrandLogoFileDisplay => _layoutStore.GetBrandLogoFileName() ?? "None";
+
+    private void BrowseBrandLogo()
+    {
+        var dialog = new Microsoft.Win32.OpenFileDialog
+        {
+            Title = "Choose brand logo",
+            Filter = "Images|*.png;*.jpg;*.jpeg;*.bmp;*.gif",
+        };
+        if (dialog.ShowDialog() != true) return;
+        _layoutStore.SetBrandLogo(File.ReadAllBytes(dialog.FileName), Path.GetFileName(dialog.FileName));
+        EnsureBrandLogos();
+        OnPropertyChanged(nameof(BrandLogoFileDisplay));
+        ScheduleSave();
+    }
+
+    internal static Source CreateBrandLogo(string? assetId) => new()
+    {
+        Name = "Brand logo",
+        Type = SourceType.Image,
+        IsBrandLogo = true,
+        IsEnabled = true,
+        AssetId = assetId,
+        X = BrandLogoX,
+        Y = BrandLogoY,
+        Width = BrandLogoWidth,
+        Height = BrandLogoHeight,
+    };
+
+    /// <summary>Exactly one brand logo per scene, placed directly above the background, carrying
+    /// the current App Settings image.</summary>
+    internal void EnsureBrandLogos()
+    {
+        var assetId = _layoutStore.GetBrandLogoAssetId();
+        foreach (var scene in Scenes)
+        {
+            var logos = scene.Elements.OfType<Source>().Where(s => s.IsBrandLogo).ToList();
+            foreach (var extra in logos.Skip(1))
+                scene.Elements.Remove(extra);
+            var logo = logos.FirstOrDefault();
+            if (logo == null)
+            {
+                var background = scene.Elements.OfType<Source>().FirstOrDefault(s => s.IsBackground);
+                var index = background == null ? 0 : scene.Elements.IndexOf(background) + 1;
+                logo = CreateBrandLogo(assetId);
+                scene.Elements.Insert(index, logo);
+            }
+            else
+            {
+                logo.AssetId = assetId;
+            }
+            _sceneGraph.InvalidateBake(scene);
+        }
+    }
+}

ViewModels/MainViewModel.Sources.cs

@@ -237,11 +237,11 @@ public partial class MainViewModel
     // session when the last using scene lets go). The webcam identity survives —
     // it's the app-level default, so removing a scene's placement re-enables Add
     // for the same camera instead of dropping it.
-    private void RemoveElement(SceneElement? element)
+    internal void RemoveElement(SceneElement? element)
     {
         var scene = StagedScene;
         if (scene == null || element == null) return;
-        if (element is Source { IsBackground: true }) return;
+        if (element is Source { IsBackground: true } or Source { IsBrandLogo: true }) return;
         if (element is WebcamSceneConfig && _webcam != null)
         {
             if (SelectedElement == element)