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
 
@@ -179,15 +183,17 @@ class HealthMonitor:
 
   private def validateStartupInstances(timeoutMs: Long): Unit =
     Thread.sleep(timeoutMs)
-    instanceRegistry.getAllInstances.foreach { inst =>
-      if !grpcServer.hasActiveStream(inst.instanceId) then
-        log.warnf(
-          "Startup: instance %s did not reconnect within %dms — evicting",
-          inst.instanceId,
-          timeoutMs,
-        )
-        instanceRegistry.removeInstance(inst.instanceId)
-        deleteK8sPod(inst.instanceId)
+    grpcServerOpt.foreach { grpcServer =>
+      instanceRegistry.getAllInstances.foreach { inst =>
+        if !grpcServer.hasActiveStream(inst.instanceId) then
+          log.warnf(
+            "Startup: instance %s did not reconnect within %dms — evicting",
+            inst.instanceId,
+            timeoutMs,
+          )
+          instanceRegistry.removeInstance(inst.instanceId)
+          deleteK8sPod(inst.instanceId)
+      }
     }
 
   private def handlePodTerminating(pod: Pod): Unit =