Fix: Migración a pyproject.toml y poetry

- Reemplaza setup.py/setup.cfg por pyproject.toml (PEP 621) + poetry.lock
- Dev dependencies en [tool.poetry.group.dev.dependencies]
- Elimina requirements_dev.txt (deps dev en pyproject.toml)
- Actualiza tox.ini, Makefile, Makefile.dev, Dockerfile y docs

Makefile

@@ -80,9 +80,8 @@ release: dist ## package and upload a release
 	twine upload dist/*
 
 dist: clean ## builds source and wheel package
-	python setup.py sdist
-	python setup.py bdist_wheel
+	python -m build
 	ls -l dist
 
 install: clean ## install the package to the active Python's site-packages
-	python setup.py install
+	pip install .