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/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Admin/RestartDriver.cs

@@ -1,5 +1,16 @@
 namespace ZB.MOM.WW.OtOpcUa.Commons.Messages.Admin;
 
+/// <summary>
+///     Shared DPS topic for driver-control commands (<see cref="RestartDriver"/>,
+///     <see cref="ReconnectDriver"/>). Publishers (AdminOperationsActor) and subscribers
+///     (DriverHostActor) reference this single constant so renames can't silently
+///     desynchronise.
+/// </summary>
+public static class DriverControlTopic
+{
+    public const string Name = "driver-control";
+}
+
 /// <summary>
 ///     AdminUI → AdminOperationsActor: restart the driver actor for one instance.
 ///     A restart fully stops and respawns the actor — loses in-memory state, may briefly

src/Core/ZB.MOM.WW.OtOpcUa.Commons/Messages/Drivers/DriverHealthChanged.cs

@@ -20,4 +20,12 @@ public sealed record DriverHealthChanged(
     DateTime? LastSuccessfulReadUtc,
     string? LastError,
     int ErrorCount5Min,
-    DateTime PublishedUtc);
+    DateTime PublishedUtc)
+{
+    /// <summary>
+    ///     DPS topic name. Both the runtime <c>AkkaDriverHealthPublisher</c> and the AdminUI
+    ///     <c>DriverStatusSignalRBridge</c> reference this single constant so renames can't
+    ///     silently desynchronise publisher and subscriber.
+    /// </summary>
+    public const string TopicName = "driver-health";
+}