Add LiteLLM RBAC: akP-litellm groups + role claim mapping

Bring LiteLLM into the two-tier RBAC and map groups to LiteLLM roles.

- akP-litellm-admin / akP-litellm-user permission groups (bound to the litellm
  app for access); added to akR-global-admin / akR-standard-user roles.
- Generic per-provider role_mappings: emit an app role claim computed from
  effective (hierarchical) group membership. LiteLLM: emits `litellm_role`
  (proxy_admin for akP-litellm-admin, internal_user for akP-litellm-user, else
  internal_user_view_only); LiteLLM reads it via GENERIC_USER_ROLE_ATTRIBUTE.

Validated: plan 5 to add, 3 to change; generated role expression renders correctly.

config/roles/akR-global-admin.yaml

@@ -3,3 +3,4 @@ permissions:
   - akP-grafana-admin
   - akP-argocd-admin
   - akP-rancher-admin
+  - akP-litellm-admin