Align the Python version floor in security-tracker-stats-dashboard

[justinmclean]

Summary

tools/security-tracker-stats-dashboard/pyproject.toml declares three different
Python version floors across its own settings.

Background

requires-python and ruff say 3.9, mypy says 3.10. mypy therefore type-checks
against a version the package claims to support running below, so a 3.10-only
construct type-checks clean and fails at import on 3.9. The >=3.9 floor also
means PEP 604 X | Y unions must stay in annotations guarded by
from __future__ import annotations, never in runtime positions.

Where to look

• pyproject.toml line 27 (requires-python = ">=3.9"), line 36 (ruff
  target-version = "py39"), line 44 ([tool.mypy] python_version = "3.10").
• Sibling tools/*/pyproject.toml show what floor the rest of the repo settles on.

Acceptance criteria

• All three settings agree on one floor.
• If the floor lands on 3.9, no runtime-position PEP 604 union remains.
• uv run --directory tools/security-tracker-stats-dashboard --group dev pytest passes.

Estimated effort

~1 hour for someone new to the codebase, plus a look for runtime unions.

[Shaurya2k06]

Easy enough, I'll take this up!
cc @justinmclean

[justinmclean]

I may have fixed this - but it would be good to double check - #965

[Shaurya2k06]

Had a look, i think you're only re-locking the root uv.lock so eight workspace members’ recorded mypy specifiers match mypy>=2.3.0. It touches no tools/security-tracker-stats-dashboard/pyproject.toml (or README), so requires-python / ruff / mypy there are still the old mixed floors.

Happy to make a fix for this.

I may have fixed this - but it would be good to double check - #965

[justinmclean]

Thanks for checking