fix: correct pod matching logic from endsWith to contains

Pod matching used endsWith(instanceId) which failed to match any pods because instanceId is randomly generated 8-char string, not pod name suffix. All instances marked dead causing cascading health check failures.

Changed to podName.contains(instanceId) to match instanceId embedded anywhere in pod name. Reverting incomplete fix from previous commit.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

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

@@ -131,7 +131,7 @@ class HealthMonitor:
 
         pods.exists { pod =>
           val podName = pod.getMetadata.getName
-          podName.endsWith(instanceId) && isPodReady(pod)
+          podName.contains(instanceId) && isPodReady(pod)
         }
       catch
         case ex: Exception =>
@@ -185,7 +185,7 @@ class HealthMonitor:
             .getItems
             .asScala
 
-          pods.find(pod => pod.getMetadata.getName.endsWith(instanceId)) match
+          pods.find(pod => pod.getMetadata.getName.contains(instanceId)) match
             case Some(pod) =>
               val podName = pod.getMetadata.getName
               kube.pods().inNamespace(config.k8sNamespace).withName(podName).withGracePeriod(0L).delete()
@@ -244,4 +244,4 @@ class HealthMonitor:
 
   private def findRegisteredInstance(pod: Pod): Option[InstanceMetadata] =
     val podName = pod.getMetadata.getName
-    instanceRegistry.getAllInstances.find(inst => podName.endsWith(inst.instanceId))
+    instanceRegistry.getAllInstances.find(inst => podName.contains(inst.instanceId))