Switch kustomize base from helmCharts to pre-rendered manifests

kustomize 5.4.3 (bundled in ArgoCD) removed localChartPath and chartPath
from its JSON schema, making helmCharts: with a local chart path invalid.
Pre-render the base manifests with 'make render-helm' instead; overlays
patch the plain YAML as before. ServiceMonitor excluded until Prometheus
is installed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

k8s/base/kustomization.yaml

@@ -1,8 +1,5 @@
 apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 
-helmCharts:
-  - name: hello-svc
-    releaseName: hello-svc
-    localChartPath: ../../helm/hello-svc
-    valuesFile: values.yaml
+resources:
+  - manifest.yaml