Two front doors: Module-level access in a Django GRC app

Introduces a pattern for module-level access control in Django applications using group membership enforcement. This involves creating a reusable `GroupRequiredMixin` in a core app that modules inherit from, and a `user_in_group` template filter for UI guards. The core app has zero knowledge of module-specific data, ensuring clean separation. This pattern is applied to a GRC tool serving Security Compliance and Internal Audit teams.