docs: restore Sealos community installation guide

Author: yangchuansheng

docs/setup/install/sealos.md

@@ -0,0 +1,70 @@
+# Sealos
+
+!!! warning "Community documentation"
+
+    This page is maintained by the Sealos templates community and is not
+    verified by headscale developers. Report deployment-specific issues in the
+    [Sealos templates repository](https://github.com/labring-actions/templates/issues).
+    Confirm that the template uses a supported headscale release before
+    production use.
+
+The community-maintained Sealos template deploys headscale and
+[Headplane](https://github.com/tale/headplane) on Kubernetes. It configures
+persistent storage, TLS-enabled endpoints, and SQLite by default. PostgreSQL is
+available as a deployment option.
+
+[![Deploy on Sealos](https://sealos.io/Deploy-on-Sealos.svg)](https://sealos.io/products/app-store/headscale)
+
+## Deploy
+
+1. Open the Sealos template and select **Deploy Now**.
+1. Keep SQLite for the default deployment, or enable PostgreSQL to provision a
+   dedicated database.
+1. Wait for the headscale and Headplane containers to become ready.
+1. Open the application URL. The root path redirects to Headplane at `/admin/`.
+
+The template also creates a separate TLS endpoint for the headscale gRPC API.
+
+## Sign in and register a node
+
+Create a headscale API key from the headscale container:
+
+```shell
+headscale apikeys create
+```
+
+Paste the key into the Headplane sign-in page. In Headplane, create a user and
+then create a pre-authentication key for that user.
+
+Connect a node with the public application URL and the pre-authentication key:
+
+```shell
+tailscale up \
+  --login-server=https://<HEADSCALE_DOMAIN> \
+  --authkey=<PRE_AUTH_KEY>
+```
+
+Continue with the [getting started guide](../../usage/getting-started.md) for
+the standard headscale registration workflow.
+
+## Persistence and database
+
+The template persists these paths:
+
+| Path                 | Contents                                 |
+| -------------------- | ---------------------------------------- |
+| `/var/lib/headscale` | SQLite database, keys, and runtime state |
+| `/etc/headscale`     | Headscale configuration                  |
+| `/var/lib/headplane` | Headplane state                          |
+
+When PostgreSQL is enabled, Sealos provisions a dedicated database and injects
+its credentials from a Kubernetes Secret. The headscale configuration and keys
+remain on persistent volumes.
+
+## Updating
+
+Review the template's
+[deployment notes](https://github.com/labring-actions/templates/tree/kb-0.9/template/headscale)
+for its currently tested headscale and Headplane versions. Before changing the
+headscale image version, back up the database and persistent volumes and follow
+the [upgrade guide](../upgrade.md).

mkdocs.yml

@@ -172,6 +172,7 @@ nav:
           - Official releases: setup/install/official.md
           - Community packages: setup/install/community.md
           - Container: setup/install/container.md
+          - Sealos (community): setup/install/sealos.md
           - Build from source: setup/install/source.md
           - Development builds: setup/install/main.md
       - Upgrade: setup/upgrade.md