[REF] Code quality improvements and structure fixes

- Add mypy.ini configuration to exclude migration scripts
- Rename migration files to proper snake_case (post-migration.py → post_migration.py)
- Add __init__.py to migration directories for proper Python package structure
- Add new portal access tests for website_sale_aplicoop
- Code formatting improvements (black, isort)
- Update copilot instructions and project configuration

Related to previous code quality refactoring work.

pyproject.toml

@@ -31,3 +31,10 @@ known_odoo = ["odoo"]
 known_odoo_addons = ["odoo.addons"]
 sections = ["FUTURE", "STDLIB", "THIRDPARTY", "ODOO", "ODOO_ADDONS", "FIRSTPARTY", "LOCALFOLDER"]
 default_section = "THIRDPARTY"
+
+[tool.mypy]
+# Excluir carpetas de migraciones y archivos de post-migrate.py que usan guiones
+# (evita errores de "Duplicate module" en mypy cuando múltiples addons contienen
+# archivos con el mismo nombre como `post-migrate.py`). Usamos una expresión
+# regular que coincide con cualquier ruta que contenga `/migrations/`.
+exclude = "(?i).*/migrations/.*"