Add NewChainPermissionProvider: tries each rbac.PermissionProvider in order,
returns the first non-zero mask, propagates errors immediately. Primary use case:
ClaimsPermissionProvider (JWT fast-path, no DB call) chained with
CachedPermissionProvider (DB fallback). Bump rbac dependency to v1.0.0.
API committed as stable.
Provides SetTokenData for upstream AuthMiddleware implementations,
EnrichmentMiddleware and AuthzMiddleware compatible with any provider that
calls SetTokenData, ClaimsPermissionProvider for JWT-embedded permissions,
and CachedPermissionProvider for TTL-backed runtime resolution via any
Cache implementation.
