fix: add kustomization for cert-manager in cluster/production

clusters/production/cert-manager.yaml

@@ -0,0 +1,17 @@
+# Datei: infrastructure/kustomization-cert-manager.yaml
+apiVersion: kustomize.toolkit.fluxcd.io/v1
+kind: Kustomization
+metadata:
+  name: cert-manager
+  namespace: flux-system
+spec:
+  interval: 10m
+  path: ../../infrastructure/cert-manager
+  prune: true
+  sourceRef:
+    kind: GitRepository
+    name: flux-system
+  decryption:
+    provider: sops
+    secretRef:
+      name: sops-gpg