feat: add audio playback and file download features with corresponding UI updates

src/EchoHub.Client/Services/AudioPlaybackService.cs

@@ -0,0 +1,39 @@
+using NetCoreAudio;
+using Serilog;
+
+namespace EchoHub.Client.Services;
+
+public class AudioPlaybackService
+{
+    private readonly Player _player = new();
+
+    public bool IsPlaying => _player.Playing;
+
+    public async Task PlayAsync(string filePath)
+    {
+        try
+        {
+            if (_player.Playing)
+                await _player.Stop();
+
+            await _player.Play(filePath);
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to play audio file: {Path}", filePath);
+        }
+    }
+
+    public async Task StopAsync()
+    {
+        try
+        {
+            if (_player.Playing)
+                await _player.Stop();
+        }
+        catch (Exception ex)
+        {
+            Log.Warning(ex, "Failed to stop audio playback");
+        }
+    }
+}