chore: manual sync for leaf apps, keep root app-of-apps automated

Convention: only the root app-of-apps (platform) auto-syncs so it picks up
new/changed child Application definitions from Git. Every leaf service app
(vault, headlamp, harbor, jenkins, sonarqube, external-secrets,
kube-prometheus-stack) now requires an explicit manual Sync — matches
cluster-bootstrap and homelab-services' existing ignis convention.

platform/apps/sonarqube/application.yaml

@@ -25,10 +25,8 @@ spec:
   destination:
     server: https://kubernetes.default.svc
     namespace: sonarqube
+  # Leaf app — manual sync only; root `platform` app-of-apps stays automated.
   syncPolicy:
-    automated:
-      prune: true
-      selfHeal: true
     syncOptions:
       - CreateNamespace=true
       - SkipDryRunOnMissingResource=true