refactor: introduce declarative permission pattern for authorization

[ppravdin]

Replace procedural authorization logic with a declarative Permission/Policy pattern. This improves code clarity, maintainability, and testability.

Key changes:

• Add Permission abstraction and concrete implementations (IsSelf, IsSuperior, etc.)
• Add composite permissions (AnyOf, AllOf) for complex authorization rules
• Extend AuthorizationService with declarative authorize() method
• Refactor ChangePasswordInteractor and GrantAdminInteractor to use new pattern

The old procedural methods are retained for backward compatibility. This change demonstrates Clean Architecture principles by improving the application layer abstractions without affecting other layers.

[ivan-borovets]

Thanks for the idea!
Moving to a declarative permission model definitely helps express authorization logic in a cleaner and more extensible way.

I did hesitate a bit over adding another abstraction layer — it can raise the entry barrier for new developers — but in the end, the gain in clarity felt worth it.

To support that direction, a few adjustments were made:

• Dropped TYPE_CHECKING since Python 3.12 handles forward references by default.
• Introduced typed context dataclasses instead of **kwargs, to make permission contracts explicit and type-safe.
• Used generics to tie permissions to their expected context types.

Let me know what you think about the current version.

[ivan-borovets]

Proceeding with this for now. Always open to feedback if anything needs to be revisited.