docs: sync README.vi.md and INSTALL.md with the systemd auto-start section

README.md already documented ccam service install/status/uninstall; the
Vietnamese mirror and the full install guide had gone stale.

INSTALL.md

@@ -187,6 +187,20 @@ npm start       # Start Express serving client/dist on port 4820
 
 Open **http://localhost:4820** in your browser.
 
+`npm start` (and `ccam start`, its backgrounded form) only run while that
+process is alive — a reboot loses it. On Linux, run the server as a systemd
+`--user` service instead so it comes back on its own after every reboot, with
+no manual step and no Claude Code (or any other tool) needed to trigger it:
+
+```bash
+ccam service install       # writes + enables ~/.config/systemd/user/ccam.service
+ccam service status        # systemctl --user status ccam
+ccam service uninstall     # disable and remove it
+```
+
+See [`README.md` → Run as a service](./README.md#run-as-a-service-auto-start-on-boot)
+and, for plugin installs, [`docs/PLUGINS.md` → Auto-start on boot](docs/PLUGINS.md#auto-start-on-boot).
+
 ---
 
 ## Optional: Local MCP server