Support PEP 668

Describe the bug

The template/component does not support Docker image applying PEP 668 https://peps.python.org/pep-0668/

Expected behavior

When I change the base image, folowing PEP 668, I expect it works.

Actual behavior

Major failure during the pip install of requirements.

Logs and/or screenshots

$ prepare_sphinx
[INFO] installing requirements from file requirements.txt
error: externally-managed-environment
× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.
    
    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.
    
    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.
    
    See /usr/share/doc/python3.12/README.venv for more information.
note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.

Context & Configuration

The image is set to ghcr.io/sphinx-doc/sphinx-ci:latest