refactor(driver-pages): address Phase 6/8 deep-review findings

- Topic-name drift fix: DriverHealthChanged.TopicName and
  DriverControlTopic.Name now live on the message contracts in
  Commons. AkkaDriverHealthPublisher, DriverStatusSignalRBridge,
  DriverHostActor, and AdminOperationsActor all delegate to the
  single constant so a rename can't silently desynchronise
  publisher and subscriber.
- DriverStatusPanel._opResultClearTimer switched from
  System.Timers.Timer to System.Threading.Timer + awaited
  DisposeAsync. Prevents an in-flight 8s clear-callback from
  invoking StateHasChanged on a component whose hub has already
  been released.
- PublishHealthSnapshot deduplicates against the last published
  (state, lastSuccess, lastError, errorCount) fingerprint. The
  30s heartbeat no longer floods the SignalR layer with identical
  Healthy snapshots — newly-joined clients still warm up via the
  snapshot store on JoinDriver.

src/Server/ZB.MOM.WW.OtOpcUa.ControlPlane/AdminOperations/AdminOperationsActor.cs

@@ -178,7 +178,7 @@ public sealed class AdminOperationsActor : ReceiveActor
         {
             // Broadcast to every DriverHostActor on every node via the driver-control DPS topic.
             // Only the host that owns the instance will act; others ignore it (id not found in _children).
-            DistributedPubSub.Get(Context.System).Mediator.Tell(new Publish("driver-control", msg));
+            DistributedPubSub.Get(Context.System).Mediator.Tell(new Publish(DriverControlTopic.Name, msg));
 
             await using var db = await _dbFactory.CreateDbContextAsync();
             db.ConfigEdits.Add(new ConfigEdit
@@ -208,7 +208,7 @@ public sealed class AdminOperationsActor : ReceiveActor
         try
         {
             // Broadcast to every DriverHostActor; only the one owning the instance reacts.
-            DistributedPubSub.Get(Context.System).Mediator.Tell(new Publish("driver-control", msg));
+            DistributedPubSub.Get(Context.System).Mediator.Tell(new Publish(DriverControlTopic.Name, msg));
 
             await using var db = await _dbFactory.CreateDbContextAsync();
             db.ConfigEdits.Add(new ConfigEdit