REFACTOR(app): change image write-back

- Switch to ArgoCD write-back method
- Update image update strategy

deploy/argocd/application.yaml

@@ -6,7 +6,7 @@ metadata:
   annotations:
     argocd-image-updater.argoproj.io/image-list: portfolio=ghcr.io/mayne0213/portfolio
     argocd-image-updater.argoproj.io/portfolio.update-strategy: latest
-    argocd-image-updater.argoproj.io/write-back-method: git
+    argocd-image-updater.argoproj.io/write-back-method: argocd
   finalizers:
     - resources-finalizer.argocd.argoproj.io
 spec: