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>

traefik/ingressclass.yaml

@@ -0,0 +1,15 @@
+---
+# Source: traefik/templates/ingressclass.yaml
+apiVersion: networking.k8s.io/v1
+kind: IngressClass
+metadata:
+  annotations:
+    ingressclass.kubernetes.io/is-default-class: "true"
+  labels:
+    app.kubernetes.io/name: traefik
+    app.kubernetes.io/instance: traefik-traefik
+    helm.sh/chart: traefik-36.1.0
+    app.kubernetes.io/managed-by: Helm
+  name: traefik
+spec:
+  controller: traefik.io/ingress-controller