fix: Register async executor as a bean using @bean

- Fixes graceful shutdown failure for @async tasks
- Ensures the executor's lifecycle is managed by Spring
- Removes redundant manual call to initialize()

Author: psh10066

core/core-api/src/main/java/io/dodn/springboot/core/api/config/AsyncConfig.java

@@ -1,6 +1,7 @@
 package io.dodn.springboot.core.api.config;
 
 import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.scheduling.annotation.AsyncConfigurer;
 import org.springframework.scheduling.annotation.EnableAsync;
@@ -12,6 +13,7 @@
 @EnableAsync
 public class AsyncConfig implements AsyncConfigurer {
 
+    @Bean
     @Override
     public Executor getAsyncExecutor() {
         ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
@@ -20,7 +22,6 @@ public Executor getAsyncExecutor() {
         executor.setQueueCapacity(10000);
         executor.setWaitForTasksToCompleteOnShutdown(true);
         executor.setAwaitTerminationSeconds(10);
-        executor.initialize();
         return executor;
     }