Read Python version from .python-version in Dockerfile and Ansible

[Copilot]

Replaces hardcoded python3.13 throughout the Dockerfile and Ansible playbook with dynamic reads from the canonical .python-version file, consistent with how .ruby-version is already consumed.

Dockerfile

• COPY .python-version .python-version added to base stage after WORKDIR, making the file available to all subsequent stages
• Each RUN that references Python reads the version inline: PYTHON_VERSION=$(cat .python-version)

COPY .python-version .python-version

RUN PYTHON_VERSION=$(cat .python-version) && \
    apt-get install ... python${PYTHON_VERSION} ...

RUN PYTHON_VERSION=$(cat .python-version) && \
    python${PYTHON_VERSION} -m ensurepip --upgrade --default-pip && \
    python${PYTHON_VERSION} -m pip install -r requirements.txt

Note: the variable is re-read per RUN step — this is unavoidable since shell variables don't persist across Docker layers.

Ansible (Deploy-SEEK.yml)

• Two tasks prepend the Python section to slurp .python-version and register it as a fact, mirroring the existing .ruby-version pattern
• All python3.13 references in package names and shell commands replaced with python{{ python_version }}

- name: Read python version from .python-version file
  ansible.builtin.slurp:
    src: '{{git_dest}}/SEEK/.python-version'
  register: python_version_file

- name: Set python version fact
  ansible.builtin.set_fact:
    python_version: "{{ python_version_file.content | b64decode | trim }}"