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>

tox.ini

@@ -3,22 +3,17 @@ isolated_build = True
 
 [testenv:linters]
 deps =
-  black
-  flake8
+  ruff
   yamllint
 allowlist_externals = make
 setenv =
-  BLACK_ARGS = --check
   PYTHON = python3
 commands =
-  make black
-  flake8 awx awxkit awx_collection
+  # awx_collection is excluded: ansible-test sanity runs its own linters which conflict with ruff
+  ruff format --check awx awxkit
+  ruff check awx awxkit
   yamllint -s .
 
-[flake8]
-select = F401,F402,F821,F823,F841,F811,E265,E266,F541,W605,E722,F822,F523,W291,F405
-exclude = env,awx_collection_build,.tox
-
 [testenv:pip-compile-docs]
 description = Compile docs build lockfiles
 deps =