fix: duration doesn't get accurately compared in alb service base (#2…

…1584)

fixes #21560

Duration wasn't getting compared correctly and prevented values above 400 from getting used for `ApplicationLoadBalancedService.idleTimeout`

----

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packages/@aws-cdk/aws-ecs-patterns/lib/base/application-load-balanced-service-base.ts

@@ -272,7 +272,7 @@ export interface ApplicationLoadBalancedServiceBaseProps {
   readonly enableExecuteCommand?: boolean;
 
   /**
-   * The load balancer idle timeout, in seconds
+   * The load balancer idle timeout, in seconds. Can be between 1 and 4000 seconds
    *
    * @default - CloudFormation sets idle timeout to 60 seconds
    */
@@ -443,7 +443,8 @@ export abstract class ApplicationLoadBalancedServiceBase extends Construct {
     const internetFacing = props.publicLoadBalancer ?? true;
 
     if (props.idleTimeout) {
-      if (props.idleTimeout > Duration.seconds(4000) || props.idleTimeout < Duration.seconds(1)) {
+      const idleTimeout = props.idleTimeout.toSeconds();
+      if (idleTimeout > Duration.seconds(4000).toSeconds() || idleTimeout < Duration.seconds(1).toSeconds()) {
         throw new Error('Load balancer idle timeout must be between 1 and 4000 seconds.');
       }
     }

packages/@aws-cdk/aws-ecs-patterns/test/ec2/l3s.test.ts

@@ -880,7 +880,7 @@ test('passes when idleTimeout is between 1 and 4000 seconds', () => {
           streamPrefix: 'TestStream',
         }),
       },
-      idleTimeout: Duration.seconds(120),
+      idleTimeout: Duration.seconds(4000),
       desiredCount: 2,
     });
   }).toBeTruthy();