Update docs/configuring-playbook-traefik.md: add a copyright header

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/configuring-playbook-traefik.md

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+SPDX-FileCopyrightText: 2023 - 2024 Slavi Pantaleev
+SPDX-FileCopyrightText: 2024 - 2025 MDAD project contributors
+SPDX-FileCopyrightText: 2024 - 2025 Suguru Hirahara
+SPDX-FileCopyrightText: 2024 Ed Geraghty
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+SPDX-License-Identifier: AGPL-3.0-or-later
+-->
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 # Configuring the Traefik reverse-proxy (optional, advanced)
 
 By default, this playbook installs and manages a [Traefik](https://doc.traefik.io/traefik/) reverse-proxy server, powered by the [ansible-role-traefik](https://github.com/mother-of-all-self-hosting/ansible-role-traefik) Ansible role for you. If that's okay, you can skip this document.