fix: enable player controls on load, clear track selection on stop and end-of-track

Add StateChanged multicast event to IPlayerService so AudioPlayerBar and TracksView
re-render themselves without relying on the IsFixed cascade re-render path. Clear
_selectedTrack in TracksView when IsLoaded drops (stop, unload, end-of-track). Set
IsLoaded=false in OnPlaybackEndCallback so end-of-track triggers the same clear path.
Add JS-module readiness probe in AudioInteropService; delete dead TS and buffered C#
path; consolidate GetPlayIcon/FormatTime helpers; fix misleading minimize dock icon.

DeepDrftPublic.Client/Services/IPlayerService.cs

@@ -22,6 +22,16 @@ public interface IPlayerService
     // Events for UI updates
     EventCallback? OnStateChanged { get; set; }
     EventCallback? OnTrackSelected { get; set; }
+
+    /// <summary>
+    /// Multicast side-channel for state changes. The provider owns the single
+    /// <see cref="OnStateChanged"/> EventCallback (it drives the provider re-render);
+    /// cascade consumers that read state directly off this service — and so are not
+    /// re-rendered by the provider's render when the cascade is <c>IsFixed</c> —
+    /// subscribe here to re-render themselves. Fires on the same cadence as
+    /// <see cref="OnStateChanged"/> (throttled to ~10/s during streaming).
+    /// </summary>
+    event Action? StateChanged;
     
     // Control methods
     Task InitializeAsync();