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.AdminUI/Hubs/DriverStatusSignalRBridge.cs

@@ -15,7 +15,7 @@ namespace ZB.MOM.WW.OtOpcUa.AdminUI.Hubs;
 /// </summary>
 public sealed class DriverStatusSignalRBridge : ReceiveActor
 {
-    public const string TopicName = "driver-health";
+    public const string TopicName = DriverHealthChanged.TopicName;
 
     private readonly IHubContext<DriverStatusHub> _hub;
     private readonly IDriverStatusSnapshotStore _store;