feat: Move cluster services to wild-directory as unified packages

Convert all 15 cluster services from embedded API format to
wild-directory packages using the unified manifest format:
- metallb, traefik, cert-manager, longhorn, snapshot-controller
- nfs, smtp, coredns, node-feature-discovery, nvidia-device-plugin
- externaldns, docker-registry, headlamp, crowdsec, utils

Changes:
- wild-manifest.yaml → manifest.yaml with is, defaultConfig, requires
- Eliminated configReferences and serviceConfig fields
- Flattened kustomize.template/ to package root
- Template vars use flat defaultConfig keys
- install.sh paths updated for apps/ layout
- Updated 9 app manifests: cloud.smtp.* → apps.smtp.* with requires
- Removed dead install: true field from 6 app manifests

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

nfs/persistent-volume.yaml

@@ -0,0 +1,23 @@
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: nfs-media-pv
+  labels:
+    storage: nfs-media
+spec:
+  capacity:
+    storage: {{ .storageCapacity }}
+  accessModes:
+    - ReadWriteMany
+  persistentVolumeReclaimPolicy: Retain
+  storageClassName: nfs
+  nfs:
+    server: {{ .host }}
+    path: {{ .mediaPath }}
+  mountOptions:
+    - nfsvers=4.1
+    - rsize=1048576
+    - wsize=1048576
+    - hard
+    - intr
+    - timeo=600