Keep an up-to-date .pre-commit-config.yaml in template subdir

[imagejan]

Our current pre-commit.ci workflow updates the .pre-commit-config.yaml in the repository root, but doesn't check the file inside the template subfolder.

Also, we should consider using ruff (both check and format), remove redundant others (e.g. black), and maybe add a ruff.toml to the project template (if we want to deviate from defaults).