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

loki/argocd.yaml

@@ -12,8 +12,8 @@ spec:
     helm:
       valueFiles:
       - $values/loki/helm-values.yaml
-  - repoURL: https://github.com/K3S-HOME/monitoring.git
-    targetRevision: HEAD
+  - repoURL: https://github.com/K3S-HOME/observability.git
+    targetRevision: main
     ref: values
   destination:
     server: https://kubernetes.default.svc