feat(health): wire up NodeHostname, ConnectionEndpoint, TagQuality, ParkedMessageCount collectors

- AkkaHostedService: SetNodeHostname from NodeOptions
- DataConnectionActor: UpdateConnectionEndpoint on state transitions,
  track per-tag quality counts and UpdateTagQuality on value changes
- HealthReportSender: query StoreAndForwardStorage for parked message count
- StoreAndForwardStorage: add GetParkedMessageCountAsync()

src/ScadaLink.Host/Actors/AkkaHostedService.cs

@@ -241,6 +241,7 @@ akka {{
 
         // Resolve the health collector for the Deployment Manager
         var siteHealthCollector = _serviceProvider.GetService<ScadaLink.HealthMonitoring.ISiteHealthCollector>();
+        siteHealthCollector?.SetNodeHostname(_nodeOptions.NodeHostname);
 
         // Create SiteReplicationActor on every node (not a singleton)
         var sfStorage = _serviceProvider.GetRequiredService<StoreAndForwardStorage>();