Add shared Python CI workflow template

[aarmey]

Summary

• Adds workflow-templates/python-uv-ruff-pytest.yml (+ properties.json), an org-wide starter workflow that shows up under "New workflow" in any meyer-lab repo's Actions tab.
• Pattern (uv sync → ruff check → ruff format --check → ty check → pytest --cov) matches what RISE, tHMM, DDMC, and parafac2 already hand-roll with slightly different names/paths — this gives new repos a consistent starting point instead of copy-pasting a slightly-different version each time.
• Does not touch any existing repo's workflows; it's opt-in per repo via the Actions UI.

Test plan

• Merge, then check a repo's Actions > New workflow page shows "Python CI (uv + ruff + pytest)" as a suggested template