feat(permission): add RBAC module with Casbin enforcement and policy reload
- Multi-tenant RBAC: permission catalog, roles, role-permission mapping,
user-role assignment, and external IdP role mapping (zitadel/ldap/scim).
- Casbin enforcer with Redis-backed adapter and Pub/Sub reload for
multi-instance policy sync; HTTP middleware enforces (tenant, role,
path, method) with platform admin bypass.
- /api/v1/permissions routes: catalog, me, policy/reload, roles CRUD,
role permissions, user roles, role mappings.
- New error scope (31) for Permission and biz code descriptions.
- Wire Permission module into ServiceContext, config, mongo-index, and
add cmd/permission-seed CLI plus etc/rbac.conf model.
- Redis client gains lazy PubSubClient helper (go-zero wrapper lacks Subscribe).
- Rewrite internal/model/member/README to cover Tenant/Member/Identity.
Co-authored-by: Cursor <cursoragent@cursor.com>
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