- Add generic CredentialStore abstraction for credential persistence
- Introduce pickle- and Redis-backed credential store implementations
- Refactor Google OAuth provider to delegate persistence to CredentialStore
- Make auth providers generic over credential type for stricter contracts
- Update package documentation to reflect credential lifecycle vs persistence split
- Add credentials module to public API surface
- Harden .gitignore to exclude credential and token artifacts
This release removes node-local persistence assumptions, enables
distributed-safe authentication, and formalizes credential storage as
a first-class extension point.
