test: use better-auth built-in test plugin
refactor: map auth errors server side
refactor: native trusted providers callback usage
<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit
## Release Notes
* **New Features**
* Enhanced SSO authentication error messaging with specific guidance for different failure scenarios (account linking required, email verification needed, banned accounts, invite-only access).
* **Chores**
* Updated authentication dependencies to version 1.5.0.
* **Tests**
* Extended test coverage for SSO error code handling and authentication scenarios.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
