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>

longhorn/README.md

@@ -0,0 +1,20 @@
+# Longhorn Storage
+
+See: [Longhorn Docs v 1.8.1](https://longhorn.io/docs/1.8.1/deploy/install/install-with-kubectl/)
+
+## Installation Notes
+
+- Manifest copied from https://raw.githubusercontent.com/longhorn/longhorn/v1.8.1/deploy/longhorn.yaml
+- Using kustomize to apply custom configuration (see `kustomization.yaml`)
+
+## Important Settings
+
+- **Number of Replicas**: Set to 1 (default is 3) to accommodate smaller clusters
+  - This avoids "degraded" volumes when fewer than 3 nodes are available
+  - For production with 3+ nodes, consider changing back to 3 for better availability
+
+## Common Operations
+
+- View volumes: `kubectl get volumes.longhorn.io -n longhorn-system`
+- Check volume status: `kubectl describe volumes.longhorn.io <volume-name> -n longhorn-system`
+- Access Longhorn UI: Set up port-forwarding with `kubectl -n longhorn-system port-forward service/longhorn-frontend 8080:80`