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.dev

@@ -15,7 +15,7 @@ dev-shell:
 	docker run --rm -ti -v "$(PWD):/app" -w /app --name facho-cli facho bash
 
 test:
-	docker run -t -v $(PWD):/app -w /app facho sh -c 'cd /app; python3.13 -m pytest'
+	docker run -t -v $(PWD):/app -w /app facho sh -c 'cd /app; python3.13 -m pytest -vv'
 
 tox:
 	docker run -it -v $(PWD)/:/app -w /app facho tox