Document and unify pre-commit hooks for Python and JavaScript

### Problem
The project's pre-commit setup is not documented, causing confusion and CI failures (e.g., in PR #906). Checks are not enforced locally for all contributors.

### Suggested Solution
1. **Unify Hooks:** Extend the existing `.pre-commit-config.yaml` to include JavaScript checks (ESLint, Prettier) alongside the Python checks (Ruff).
2. **Document Setup:** Create a `CONTRIBUTING.md` or update `DEVELOP.md` to instruct contributors on how to install and use the hooks with `uv run pre-commit install`.