fix: CI linting and deployment rules
- Re-formatted tools/run_gsifi_governance_checks.py to pass black, flake8 (E501), and mypy.
- Restored _headers and _redirects to repository root with trailing newlines.
- Ensured next-app/next.config.js follows Standard JS style.
Co-authored-by: OneFineStarstuff <87420139+OneFineStarstuff@users.noreply.github.com>