Add k8s deployment, standalone app Dockerfile.

Tested with Rancher k3s. See k8s/README.md for site configuration and
deployment instructions.

Add cert-manager, tls, remote headscale script.

k8s/postgres/kustomization.yaml

@@ -0,0 +1,13 @@
+namespace: headscale
+bases:
+- ../base
+resources:
+- deployment.yaml
+- postgres-service.yaml
+- postgres-statefulset.yaml
+generatorOptions:
+  disableNameSuffixHash: true
+secretGenerator:
+- name: postgresql
+  files:
+  - secrets/password