doc: point to 3.14.4 in all places and add a comment

README.rst

@@ -54,6 +54,7 @@ Copy/paste script:
 
   source /gpfs/exfel/sw/calsoft/.pyenv/bin/activate
   git clone ssh://git@git.xfel.eu:10022/detectors/pycalibration.git
+  git checkout 3.14.4  # Use this version for compatibility with Python 3.8.18
   cd pycalibration
   pyenv shell 3.8.18
   python3 -m venv .venv
@@ -72,7 +73,7 @@ will downgrade/upgrade your local packages, which may cause major issues and may
 installation method instead.
 
 1. ``source /gpfs/exfel/sw/calsoft/.pyenv/bin/activate``
-2. ``git clone ssh://git@git.xfel.eu:10022/detectors/pycalibration.git && cd pycalibration`` - clone the offline calibration package from EuXFEL GitLab
+2. ``git --branch 3.14.4 clone ssh://git@git.xfel.eu:10022/detectors/pycalibration.git && cd pycalibration`` - clone the offline calibration package from EuXFEL GitLab
 3. ``pyenv shell 3.8.18`` - load required version of python
 4. ``pip install .`` - install the pycalibration package (add ``-e`` flag for editable development installation)
 5. ``export PATH=$HOME/.local/bin:$PATH`` - make sure that the home directory is in the PATH environment variable
@@ -83,6 +84,7 @@ Copy/paste script:
 
   source /gpfs/exfel/sw/calsoft/.pyenv/bin/activate
   git clone ssh://git@git.xfel.eu:10022/detectors/pycalibration.git
+  git checkout 3.14.4  # Use this version for compatibility with Python 3.8.18
   pyenv shell 3.8.18
   cd pycalibration
   pip install --user .  # `-e` flag for editable install, e.g. `pip install -e .`

docs/development/installation.md

@@ -43,6 +43,7 @@ Copy/paste script:
 ```bash
 source /gpfs/exfel/sw/calsoft/.pyenv/bin/activate
 git clone ssh://git@git.xfel.eu:10022/detectors/pycalibration.git
+git checkout 3.14.4  # Use this version for compatibility with Python 3.8.18
 cd pycalibration
 pyenv shell 3.8.18
 python3 -m venv .venv