REFACTOR(repo): observability repo structure

- Add application.yaml for ArgoCD app-of-apps
- Add kustomization.yaml with observability components
- Add renovate.json for automated updates
- Update all component argocd.yaml repoURLs to observability repo

Components: prometheus, alertmanager, grafana, loki, promtail,
node-exporter, kube-state-metrics, goldilocks, uptime-kuma, vpa

kustomization.yaml

@@ -0,0 +1,15 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+
+resources:
+  - application.yaml
+  - prometheus/argocd.yaml
+  - alertmanager/argocd.yaml
+  - grafana/argocd.yaml
+  - loki/argocd.yaml
+  - promtail/argocd.yaml
+  - node-exporter/argocd.yaml
+  - kube-state-metrics/argocd.yaml
+  - goldilocks/argocd.yaml
+  - uptime-kuma/argocd.yaml
+  - vpa/argocd.yaml