[chore] Stricter ruff rules (#282)

* [chore] Stricter ruff rules

* [chore] Furture lint rules and removal of flake8

* [ci] Bump github action versions

* [chore] Add additional test coverage

* Revert RNG switch to np.random.default_rng()

Restore use of the global np.random state in pseudo_Obs (misc.py) and the
prior id generation (fits.py), keeping seed behavior unchanged. The switch
to a module-local generator is out of scope for this lint-focused PR.

* Silence NPY002 on intentional legacy np.random calls

The RNG migration was reverted to keep np.random.seed() behavior, so add
per-line noqa: NPY002 on the three legacy np.random calls instead of the
Generator API.

* [Fix] Fix exception messages

setup.py

@@ -26,7 +26,7 @@ setup(name='pyerrors',
       packages=find_packages(),
       python_requires='>=3.10.0',
       install_requires=['numpy>=2.0', 'autograd>=1.7.0', 'numdifftools>=0.9.41', 'matplotlib>=3.9', 'scipy>=1.13', 'iminuit>=2.28', 'h5py>=3.11', 'lxml>=5.0', 'python-rapidjson>=1.20', 'pandas>=2.2', 'odrpack>=0.5'],
-      extras_require={'test': ['pytest', 'pytest-cov', 'pytest-benchmark', 'hypothesis', 'nbmake', 'flake8']},
+      extras_require={'test': ['pytest', 'pytest-cov', 'pytest-benchmark', 'hypothesis', 'nbmake']},
       classifiers=[
           'Development Status :: 5 - Production/Stable',
           'Intended Audience :: Science/Research',