docs(hytale): add Hytale server page

SUMMARY.md

@@ -40,6 +40,7 @@
   * [Counter-Strike: Global Offensive](game-servers/counter-strike-global-offensive.md)
   * [Factorio](game-servers/factorio.md)
   * [Garry's Mod](game-servers/garrys-mod/README.md)
+  * [Hytale](game-servers/hytale.md)
   * [Insurgency: SandStorm](game-servers/insurgency-sandstorm.md)
   * [Killing Floor 2](game-servers/killing-floor-2.md)
   * [Minecraft: Java Edition](game-servers/minecraft.md)

game-servers/hytale.md

@@ -0,0 +1,97 @@
+# Hytale
+
+## Requirements
+
+* A **Hytale account that owns the game**. It's needed even to download the dedicated server, and for the server itself to run.
+* Java 25 (`openjdk-25-jre`). LinuxGSM installs it as a dependency.
+* At least 4 GB of RAM. The download is about 3.5 GB.
+
+Hytale isn't on Steam. LinuxGSM downloads the server with Hytale's official `hytale-downloader`.
+
+## Two One-Time Logins
+
+A Hytale server needs two separate logins with your Hytale account. Each one is approved **once** in a browser, then saved and renewed automatically.
+
+| Login | When | Saved in |
+| ----- | ---- | -------- |
+| **Downloader** | During `install` | `serverfiles/.hytale-downloader-credentials.json` |
+| **Server** | On the first `start` | `serverfiles/Server/auth.enc` (encrypted) |
+
+{% hint style="info" %}
+Both files contain credentials for your Hytale account. Like `secrets-*.cfg`, they're included in LinuxGSM backups, so keep backups private.
+{% endhint %}
+
+The server login is encrypted with a key tied to the machine, so it only works on the machine (or container) where it was created. After restoring a backup on another machine, or re-creating a Docker container, the server can't read it and needs a new login. LinuxGSM detects this on start and shows a new server login URL.
+
+## Installing
+
+1. Create and install the server:
+
+   ```
+   ./linuxgsm.sh hytserver
+   ./hytserver install
+   ```
+
+2. **Downloader login.** The install stops at **Hytale account login required** and shows a URL. Open it in a browser, log in with your Hytale account and approve the code. The install waits up to 15 minutes, then downloads and extracts the server.
+
+3. Start the server:
+
+   ```
+   ./hytserver start
+   ```
+
+4. **Server login.** On the first start, LinuxGSM shows **Hytale server login required** with a URL, and sends it as an alert if [alerts](../alerts/README.md) are configured. Open the URL and approve it within 10 minutes. The server saves the login and restores it on every restart. LinuxGSM checks this on every start and shows a new URL whenever the server isn't logged in.
+
+If the server login code expires, or you need to log in again, send the command to the server console and approve the code shown in the console log (`./hytserver console`):
+
+```
+./hytserver send "/auth login device"
+```
+
+## Docker
+
+The flow is the same, but there's no terminal, so the login URLs appear in the container logs:
+
+1. Start the container and follow its logs:
+
+   ```
+   docker logs -f hytserver
+   ```
+
+2. Approve the **downloader** login URL from the logs within 15 minutes. The install then completes.
+3. When the server starts, approve the **server** login URL from the logs, or from your configured alert (Discord, ntfy and so on), within 10 minutes.
+
+The **downloader** login is saved under `serverfiles` on the data volume, so re-creating or updating the container doesn't ask for it again. The **server** login is tied to the container, so after re-creating or updating the container, approve the new server login URL from the logs or your alert.
+
+## Server Settings
+
+The server creates `serverfiles/Server/config.json` on first start. Stop the server before editing it.
+
+| Setting      | Description                        |
+| ------------ | ---------------------------------- |
+| `ServerName` | Name shown to players.             |
+| `Password`   | Password to join. Empty for none.  |
+| `MaxPlayers` | Maximum number of players.         |
+| `MOTD`       | Message of the day.                |
+
+`./hytserver details` shows the server name, password and max players from this file.
+
+To use a different patchline (for example pre-release), set `hytalepatchline` in your LinuxGSM instance config.
+
+## Ports
+
+| Description | Port   | Protocol |
+| ----------- | ------ | -------- |
+| Game        | `5520` | UDP      |
+
+To change the port, set `port` in your LinuxGSM instance config (`lgsm/config-lgsm/hytserver/hytserver.cfg`). It's passed to the server as `--bind`.
+
+## Updates
+
+`./hytserver update` and `./hytserver check-update` use the saved downloader login, so they run unattended, for example from cron or with `updateonstart="on"`. LinuxGSM keeps your world, `config.json`, mods, bans and the server login when it updates.
+
+If the saved downloader login stops working, an unattended update fails within 5 minutes with a message, rather than waiting forever. Run `./hytserver update` in a terminal and approve the login again.
+
+{% hint style="info" %}
+The Hytale server also checks for updates itself, every hour. If it updates its own files, `./hytserver details` and `update` warn that the server files are newer than LinuxGSM's record, and the next `./hytserver update` corrects it.
+{% endhint %}