build: uv dependency groups + lockfile; untrack generated _version.py

- dev tools move from a published extra to [dependency-groups]
- uv.lock resolves one lock across CPython 3.8-3.14
- pytest config moves into pyproject (testpaths)
- explicit packages list; license classifier corrected to MIT-0
- drop obsolete setup.cfg and tests/pytest.ini

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -20,7 +20,7 @@ authors = [
 keywords = ["cli", "logging", "application"]
 classifiers = [
     "Programming Language :: Python :: 3",
-    "License :: OSI Approved :: MIT License",
+    "License :: OSI Approved :: MIT No Attribution License (MIT-0)",
     "Operating System :: OS Independent"
 ]
 
@@ -31,12 +31,21 @@ repository = "https://git-repos.zavage.net/Zavage-Software/app_skellington"
 documentation = "https://git-repos.zavage.net/Zavage-Software/app_skellington"
 
 
-[project.optional-dependencies]
+[dependency-groups]
 dev = [
-    "ruff==0.16.10",
+    "ruff==0.16.10",  # keep equal to rev in .pre-commit-config.yaml
+    "pytest",
     "pre-commit",
+    "pyyaml",         # tests/test_ci_workflow.py
 ]
 
+[tool.setuptools]
+packages = ["app_skellington"]
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+filterwarnings = ["ignore::DeprecationWarning"]
+
 [tool.setuptools_scm]
 version_file = "app_skellington/_version.py"
 version_scheme = "release-branch-semver"