Adds .flake8 config and registers the flake8 pre-commit hook scoped to
python/ at rev 7.3.0. Baseline ignore rules (E501, F401, F541, F841,
E722, E402, E741, F811, F821, F824, E231) suppress existing violations
so the hook passes cleanly on the current codebase.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
