[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.

website_sale_aplicoop/tests/test_templates_rendering.py

@@ -4,7 +4,6 @@
 from datetime import date
 from datetime import timedelta
 
-from odoo import _
 from odoo.tests.common import TransactionCase
 from odoo.tests.common import tagged
 
@@ -82,9 +81,7 @@ class TestTemplatesRendering(TransactionCase):
     def test_day_names_context_is_provided(self):
         """Test that day_names context is provided by the controller method."""
         # Simulate what the controller does, passing env for test context
-        from odoo.addons.website_sale_aplicoop.controllers.website_sale import (
-            AplicoopWebsiteSale,
-        )
+        from ..controllers.website_sale import AplicoopWebsiteSale
 
         controller = AplicoopWebsiteSale()
         day_names = controller._get_day_names(env=self.env)