Guard natsRqueueWorkerRegistry on @ConditionalOnBean(RqueueConfig.class)

The bean requires RqueueConfig but the ApplicationContextRunner in
RqueueNatsAutoConfigTest doesn't provide it, causing the context to fail
before the MessageBroker bean can be verified. Adding
@ConditionalOnBean(RqueueConfig.class) makes the registry back off in
narrow test contexts while remaining fully active in real Spring Boot apps
where RqueueConfig is always present.

Assisted-By: Claude Code

Author: sonus21

rqueue-spring-boot-starter/src/main/java/com/github/sonus21/rqueue/spring/boot/RqueueNatsAutoConfig.java

@@ -30,6 +30,7 @@
 import java.io.IOException;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -166,6 +167,7 @@ public com.github.sonus21.rqueue.worker.WorkerRegistryStore natsWorkerRegistrySt
   }
 
   @Bean
+  @ConditionalOnBean(com.github.sonus21.rqueue.config.RqueueConfig.class)
   @ConditionalOnMissingBean(com.github.sonus21.rqueue.worker.RqueueWorkerRegistry.class)
   public com.github.sonus21.rqueue.worker.RqueueWorkerRegistry natsRqueueWorkerRegistry(
       com.github.sonus21.rqueue.config.RqueueConfig rqueueConfig,