feat(logging): add DEBUG/INFO/WARN logging across services (NCS-72)

Add org.jboss.logging.Logger to AccountService, BotRegistry,
BotEventResource, InstanceRegistry, GameRedisSubscriberManager,
GameRedisPublisher, GameWebSocketResource, UserWebSocketResource.
Replace System.err.println with structured log.warnf in
GameRedisSubscriberManager. Silent exception swallow in
InstanceRegistry now emits WARN.

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

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

@@ -9,6 +9,7 @@ import com.fasterxml.jackson.databind.ObjectMapper
 import de.nowchess.coordinator.dto.InstanceMetadata
 import java.util.concurrent.ConcurrentHashMap
 import io.smallrye.mutiny.Uni
+import org.jboss.logging.Logger
 
 @ApplicationScoped
 class InstanceRegistry:
@@ -18,6 +19,7 @@ class InstanceRegistry:
   private var redisPrefix                    = "nowchess"
   // scalafix:on DisableSyntax.var
 
+  private val log       = Logger.getLogger(classOf[InstanceRegistry])
   private val mapper    = ObjectMapper()
   private val instances = ConcurrentHashMap[String, InstanceMetadata]()
 
@@ -41,7 +43,9 @@ class InstanceRegistry:
           val metadata = mapper.readValue(value, classOf[InstanceMetadata])
           instances.put(instanceId, metadata)
           Uni.createFrom().item(())
-        catch case _: Exception => Uni.createFrom().item(())
+        catch case ex: Exception =>
+          log.warnf(ex, "Failed to parse instance metadata for %s", instanceId)
+          Uni.createFrom().item(())
       }
       .onFailure()
       .recoverWithItem(())