docs: document systemd-based auto-disable of Tailscale Funnel on boot

octoprint_tailscale_funnel/README.md

@@ -85,6 +85,43 @@ sudo tailscale funnel reset
 
 Enabling Funnel makes your OctoPrint instance accessible from the public internet. Only enable it when needed and disable it when finished. The plugin will show a confirmation dialog before enabling Funnel if the "Confirm Enable" option is checked.
 
+### Disable Funnel automatically on system boot (systemd)
+
+If you prefer to make sure the Tailscale Funnel is always off after a system reboot (independent of the plugin), you can add a small systemd unit that disables Funnel shortly after boot:
+
+1) Create unit file:
+```bash
+sudo tee /etc/systemd/system/octoprint-tailscale-funnel-off.service >/dev/null <<'UNIT'
+[Unit]
+Description=Disable Tailscale Funnel after boot
+After=network-online.target tailscaled.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+User=octoprint
+ExecStart=/usr/bin/tailscale funnel reset
+# Optional: also turn off possible serve mappings on common ports
+ExecStart=/usr/bin/tailscale serve --http=80 off
+ExecStart=/usr/bin/tailscale serve --https=80 off
+
+[Install]
+WantedBy=multi-user.target
+UNIT
+```
+
+2) Enable and test:
+```bash
+sudo systemctl daemon-reload
+sudo systemctl enable --now octoprint-tailscale-funnel-off.service
+sudo systemctl status octoprint-tailscale-funnel-off.service
+```
+
+Notes:
+- Adjust `User=octoprint` if your OctoPrint runs under a different user (e.g. `pi`).
+- If sudo is required for tailscale on your system, add the corresponding sudoers entry as described above.
+- You can add a short delay by inserting `ExecStartPre=/bin/sleep 5` if Tailscale comes up late during boot.
+
 ## API Endpoints
 
 The plugin exposes the following API endpoints: