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>

cert-manager/letsencrypt-prod-dns01.yaml

@@ -0,0 +1,25 @@
+---
+apiVersion: cert-manager.io/v1
+kind: ClusterIssuer
+metadata:
+  name: letsencrypt-prod
+spec:
+  acme:
+    email: {{ .email }}
+    privateKeySecretRef:
+      name: letsencrypt-prod
+    server: https://acme-v02.api.letsencrypt.org/directory
+    solvers:
+    # DNS-01 solver for wildcard certificates
+    - dns01:
+        cloudflare:
+          apiTokenSecretRef:
+            name: cloudflare-api-token
+            key: api-token
+      selector:
+        dnsZones:
+        - "{{ .cloudflareDomain }}"
+    # Keep the HTTP-01 solver for non-wildcard certificates
+    - http01:
+        ingress:
+          class: traefik