fix(deployment): update label to use standardized format

Change the labels for the cron-checker application in the 
deployment configuration to adhere to Kubernetes' recommended 
labeling conventions. This improves consistency and allows 
better integration with tools that rely on standardized 
labels for application management.

example/deploy.yaml

@@ -34,12 +34,12 @@ apiVersion: apps/v1
 kind: Deployment
 metadata:
   labels:
-    app: cron-checker
+    app.kubernetes.io/name: cron-checker
   name: cron-checker
 spec:
   selector:
     matchLabels:
-      app: cron-checker
+      app.kubernetes.io/name: cron-checker
   strategy:
     rollingUpdate:
       maxSurge: 1
@@ -48,7 +48,7 @@ spec:
   template:
     metadata:
       labels:
-        app: cron-checker
+        app.kubernetes.io/name: cron-checker
     spec:
       serviceAccountName: cron-checker
       containers: