chore! remove support for python 3.8

[tekumara]

as it has reached EOL

fixes:

❯ make clean test
rm -rf .venv
PATH=${PATH#${VIRTUAL_ENV}/bin:} python3 -m venv --clear .venv
.venv/bin/python --version
Python 3.8.20
uv pip install -e '.[dev]'
  × No solution found when resolving dependencies:
  ╰─▶ Because the current Python version (3.8.20) does not satisfy Python>=3.9 and importlib-resources==6.5.2 depends on Python>=3.9, we can conclude that
      importlib-resources==6.5.2 cannot be used.
      And because aec-cli==3.2.2.dev8+ge70bca2.d20250401 depends on importlib-resources==6.5.2, we can conclude that aec-cli==3.2.2.dev8+ge70bca2.d20250401
      cannot be used.
      And because only aec-cli[dev]==3.2.2.dev8+ge70bca2.d20250401 is available and you require aec-cli[dev], we can conclude that your requirements are
      unsatisfiable.
make: *** [.venv] Error 1