feat(public): add Theater Mode to release detail pages

Toggle left of the lava popover hides release content so the visualizer fills
the surface; player bar grows to carry the playing release's cover, title, and
share. State on WaveformVisualizerControlState; pages and bar observe it.

DeepDrftPublic.Client/Pages/CutDetailBase.cs

@@ -1,4 +1,5 @@
 using DeepDrftModels.DTOs;
+using DeepDrftPublic.Client.Services;
 using DeepDrftPublic.Client.ViewModels;
 using Microsoft.AspNetCore.Components;
 
@@ -19,6 +20,10 @@ public abstract class CutDetailBase : ComponentBase, IDisposable
     [Inject] public required CutDetailViewModel ViewModel { get; set; }
     [Inject] public required PersistentComponentState PersistentState { get; set; }
 
+    // Theater Mode (Phase 20). The page owns the @if (!VisualizerControlState.TheaterMode) content gate,
+    // so it must re-render when the flag flips on the toggle. Property-injected; no constructor growth.
+    [Inject] public required WaveformVisualizerControlState VisualizerControlState { get; set; }
+
     private PersistingComponentStateSubscription _persistingSubscription;
 
     // The release EntryKey the ViewModel currently holds — tracks param-only navigations (e.g.
@@ -28,7 +33,12 @@ public abstract class CutDetailBase : ComponentBase, IDisposable
     private bool _loaded;
 
     protected override void OnInitialized()
-        => _persistingSubscription = PersistentState.RegisterOnPersisting(Persist);
+    {
+        _persistingSubscription = PersistentState.RegisterOnPersisting(Persist);
+        VisualizerControlState.Changed += OnVisualizerStateChanged;
+    }
+
+    private void OnVisualizerStateChanged() => InvokeAsync(StateHasChanged);
 
     protected override async Task OnParametersSetAsync()
     {
@@ -61,7 +71,11 @@ public abstract class CutDetailBase : ComponentBase, IDisposable
         return Task.CompletedTask;
     }
 
-    public void Dispose() => _persistingSubscription.Dispose();
+    public void Dispose()
+    {
+        _persistingSubscription.Dispose();
+        VisualizerControlState.Changed -= OnVisualizerStateChanged;
+    }
 
     // JSON-serializable bridge payload. Round-trips through PersistentComponentState's serializer.
     protected sealed record BridgedCut(ReleaseDto Release, IReadOnlyList<TrackDto> Tracks);