REFACTOR(repo): move vault/ to manifests/

- Move ExternalSecret files from vault/ to manifests/secret.yaml
- Merge multiple secrets with --- separator (immich)
- Update kustomization.yaml references
- Remove vault/ folders

Apps: umami, immich, code-server

umami/kustomization.yaml

@@ -1,5 +1,5 @@
 apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 resources:
-- vault/umami-password.yaml
+- manifests/secret.yaml
 - manifests/ingress.yaml