[drunc] Set up some basic formatting and linting

[jamesturner246]

It was discussed with @plasorak some time ago that we could start bringing in some automated linting and formatting to the backend drunc repo.

One nice candidate to begin with is ruff. set up a pre-commit hook for ruff linting and formatting.

Note: go easy at first. One of the concerns was that too much code would change at once. Start with a few non-controversial rules.