REFACTOR(repo): platform repo structure

- Add application.yaml for ArgoCD app-of-apps
- Add kustomization.yaml with platform components
- Add renovate.json for automated updates
- Update cert-manager/argocd.yaml repoURL to platform repo
- Update traefik/argocd.yaml repoURL to platform repo

kustomization.yaml

@@ -0,0 +1,11 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  # App of Apps Application
+  - application.yaml
+  - cert-manager/argocd.yaml
+  - traefik/argocd.yaml
+
+  # ArgoCD configuration (no Application, just configuration)
+  - argocd