Introduce a user -> role -> [permissions] model for app access and roles,
managed declaratively.
- Permission groups (akP-<app>-<access>) under config/permissions/: atomic units,
each names the application it grants access to.
- Role groups (akR-<role>) under config/roles/: what users are assigned to;
each nests permission groups via parents (akR-global-admin -> all *-admin,
akR-standard-user -> all *-user). Split into a separate authentik_group
resource so roles can reference permission ids without self-reference.
- Policy bindings gate each application to its permission groups (and, via
child->parent membership propagation, the roles that nest them).
- Hierarchical `groups` scope mapping: walks user groups up through .parents so
the OIDC claim includes inherited permission groups (works around
goauthentik/authentik#15579). Inert until a provider requests the `groups`
scope, so no behaviour change to existing apps until they opt in.
Validated with `tofu validate`.
