AAP-85334: Replace Black + Flake8 with Ruff

Migrate Python linting and formatting toolchain from Black (formatter)
and Flake8 (linter) to Ruff, which provides both in a single tool.

- pyproject.toml: remove [tool.black], add [tool.ruff] config sections
- tox.ini: replace black+flake8 deps/commands with ruff in linters env
- awxkit/tox.ini: replace flake8 with ruff in lint env
- Makefile: replace `black` target with `format` + `lint`, keep `black`
  as legacy alias, update `check` and `api-lint`
- pre-commit.sh: use `ruff format --check`, honor AWX_IGNORE_RUFF
- requirements_dev.txt: swap black/flake8 for ruff
- Dockerfile.j2: install ruff instead of black
- CONTRIBUTING.md: update tool references
- Fix noqa comments to use # separator instead of ; (ruff requirement)
- Add noqa: F841 for false positive in awxkit/cli/__init__.py

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

requirements/requirements_dev.txt

@@ -6,7 +6,7 @@ openapi-spec-validator  # OpenAPI 3.0 schema validation
 # pprofile - re-add once https://github.com/vpelletier/pprofile/issues/41 is addressed
 ipython>=7.31.1 # https://github.com/ansible/awx/security/dependabot/30
 unittest2
-black
+ruff
 pytest!=7.0.0
 pytest-asyncio
 pytest-cov
@@ -21,7 +21,6 @@ jupyter
 backports.tempfile  # support in unit tests for py32+ tempfile.TemporaryDirectory
 gprof2dot
 atomicwrites
-flake8
 yamllint
 pip>=25.3 # PEP 660 – Editable installs for pyproject.toml based builds (wheel based)
 awx-tui