fix: update grpcServer variable to use Instance wrapper and add optional access method

modules/coordinator/src/main/scala/de/nowchess/coordinator/service/HealthMonitor.scala

@@ -39,7 +39,7 @@ class HealthMonitor:
   private var meterRegistry: MeterRegistry = uninitialized
 
   @Inject
-  private var grpcServer: CoordinatorGrpcServer = uninitialized
+  private var grpcServerInstance: Instance[CoordinatorGrpcServer] = uninitialized
 
   @Inject
   private var failoverService: FailoverService = uninitialized
@@ -52,6 +52,10 @@ class HealthMonitor:
     if kubeClientInstance.isUnsatisfied then None
     else Some(kubeClientInstance.get())
 
+  private def grpcServerOpt: Option[CoordinatorGrpcServer] =
+    if grpcServerInstance.isUnsatisfied then None
+    else Some(grpcServerInstance.get())
+
   def setRedisPrefix(prefix: String): Unit =
     redisPrefix = prefix
 
@@ -179,6 +183,7 @@ class HealthMonitor:
 
   private def validateStartupInstances(timeoutMs: Long): Unit =
     Thread.sleep(timeoutMs)
+    grpcServerOpt.foreach { grpcServer =>
       instanceRegistry.getAllInstances.foreach { inst =>
         if !grpcServer.hasActiveStream(inst.instanceId) then
           log.warnf(
@@ -189,6 +194,7 @@ class HealthMonitor:
           instanceRegistry.removeInstance(inst.instanceId)
           deleteK8sPod(inst.instanceId)
       }
+    }
 
   private def handlePodTerminating(pod: Pod): Unit =
     findRegisteredInstance(pod).foreach { inst =>