Support Plone 6.2 and Python 3.14; native namespace

[ericof]

Summary

Modernization sweep bringing the add-on up to the current Plone and Python baselines, plus supporting refactors and a major version bump.

Changes

• Native namespace — converted the package to a PEP 420 native namespace, dropping the legacy pkg_resources declarations.
• Platform support — added Plone 6.2 and Python 3.14, dropped Plone 6.0 and Python 3.10 (updated CI matrix, classifiers, requires-python, and ruff target).
• Logger consolidation — moved the logger to pas.plugins.authomatic.logger, removed log.py, and modernized the INavigationRoot import to plone.base.
• Tests — reused the built-in anon_request and functional_portal fixtures from pytest-plone 1.0.0.
• Tooling — refreshed the Makefile build flow and editor configuration.
• Version — bumped to 3.0.0.dev0 to reflect the breaking support changes.

Closes

Closes #105
Closes #106
Closes #107
Closes #108
Closes #109