- Add excluded_product_ids field for explicit product exclusion
- Blacklist has absolute priority over all inclusion sources (product_ids, category_ids, supplier_ids)
- Update _get_products_for_group_order() with blacklist filter logic
- Rename 'Associations' section to 'Catálogo de Productos' with subsections:
* Productos Incluidos (whitelist: suppliers, categories, direct products)
* Productos Excluidos (blacklist: explicit exclusions)
- Add comprehensive test suite (TestProductBlacklist class with 7 tests)
- Add Spanish and Euskera translations
- Update available_products_count computation to include excluded_product_ids
- Version bump to 18.0.1.4.0
Use case: Bulk inclusion via categories/suppliers + fine-grained exclusion via blacklist
Example: Select a category with 100 products, exclude 5 unwanted → 95 available
