docs: add systemd setup guide

Author: grinev

README.md

@@ -99,6 +99,8 @@ opencode-telegram stop
 
 > Built-in daemon mode is intended for standalone npm installs without an external supervisor. For `systemd`, `pm2`, or Docker, keep using `opencode-telegram start` without `--daemon`.
 
+For Linux `systemd` setup, see [`docs/LINUX_SYSTEMD_SETUP.md`](./docs/LINUX_SYSTEMD_SETUP.md).
+
 To reconfigure at any time:
 
 ```bash

docs/LINUX_SYSTEMD_SETUP.md

@@ -0,0 +1,84 @@
+# Linux systemd setup
+
+## 1. Install and configure the bot
+
+```bash
+npm install -g @grinev/opencode-telegram-bot@latest
+opencode-telegram config
+```
+
+## 2. Get the required paths
+
+```bash
+which node
+which opencode-telegram
+dirname "$(which node)"
+```
+
+Use these values in the service file:
+
+- `<USER>`: your Linux user
+- `<NODE_PATH>`: output of `which node`
+- `<OPENCODE_TELEGRAM_PATH>`: output of `which opencode-telegram`
+- `<NODE_BIN_DIR>`: output of `dirname "$(which node)"`
+
+## 3. Create the service file
+
+Create `/etc/systemd/system/opencode-telegram-bot.service`:
+
+```ini
+[Unit]
+Description=OpenCode Telegram Bot
+After=network.target
+
+[Service]
+Type=simple
+User=<USER>
+Environment=PATH=<NODE_BIN_DIR>:/usr/local/bin:/usr/bin:/bin
+ExecStart=<NODE_PATH> <OPENCODE_TELEGRAM_PATH> start
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Run the bot in foreground mode. Do not use `--daemon` under `systemd`.
+
+## 4. Enable and start the service
+
+```bash
+sudo systemctl daemon-reload
+sudo systemctl enable opencode-telegram-bot
+sudo systemctl start opencode-telegram-bot
+sudo systemctl status opencode-telegram-bot
+```
+
+## 5. View logs
+
+```bash
+sudo journalctl -u opencode-telegram-bot -f
+```
+
+## Example
+
+This is a working example for an `nvm`-based setup:
+
+`ExecStart` does not include `start` here because `start` is the default CLI command.
+
+```ini
+[Unit]
+Description=OpenCode Telegram Bot
+After=network.target
+
+[Service]
+Type=simple
+User=admin
+Environment=PATH=/home/admin/.nvm/versions/node/v20.20.2/bin:/usr/local/bin:/usr/bin:/bin
+ExecStart=/home/admin/.nvm/versions/node/v20.20.2/bin/node /home/admin/.nvm/versions/node/v20.20.2/bin/opencode-telegram
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=default.target
+```