fix(session): tie directory ownership to the live connection

Ownership is claimed with a Lua check-and-set keyed on the instance holding
the websocket, routing prefers a live controller over a local copy, the
session list deduplicates by owner, removal is ownership-checked, undelivered
routed messages surface, single-session lookups stop scanning the keyspace and
directory writes leave the request path bounded by a timeout.

Emby.Server.Implementations/Session/RedisPodMessageBus.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Text.Json;
+using System.Threading;
 using System.Threading.Tasks;
 using Jellyfin.Extensions.Json;
 using MediaBrowser.Controller.Session;
@@ -16,6 +17,8 @@ public sealed class RedisPodMessageBus : IPodMessageBus
 {
     private const string ChannelPrefix = "jellyfin:pod:";
 
+    private static readonly TimeSpan _publishTimeout = TimeSpan.FromSeconds(5);
+
     private static readonly JsonSerializerOptions _jsonOptions = JsonDefaults.Options;
 
     private readonly ISubscriber _subscriber;
@@ -39,7 +42,7 @@ public sealed class RedisPodMessageBus : IPodMessageBus
     public string PodId { get; }
 
     /// <inheritdoc />
-    public void Publish(string targetPod, PodMessage message)
+    public async Task<long> PublishAsync(string targetPod, PodMessage message, CancellationToken cancellationToken = default)
     {
         ArgumentException.ThrowIfNullOrEmpty(targetPod);
         ArgumentNullException.ThrowIfNull(message);
@@ -48,14 +51,14 @@ public sealed class RedisPodMessageBus : IPodMessageBus
 
         try
         {
-            _subscriber.Publish(
+            return await _subscriber.PublishAsync(
                 RedisChannel.Literal(ChannelPrefix + targetPod),
-                JsonSerializer.Serialize(message, _jsonOptions),
-                CommandFlags.FireAndForget);
+                JsonSerializer.Serialize(message, _jsonOptions)).WaitAsync(_publishTimeout, cancellationToken).ConfigureAwait(false);
         }
         catch (Exception ex)
         {
             _logger.LogWarning(ex, "Failed to send a {Kind} message to {TargetPod}.", message.Kind, targetPod);
+            return 0;
         }
     }