v1.5.0 of authsome

Dart client SDK for the Authsome authentication platform. Provides a typed HTTP client and request/response models for sign-in, sessions, MFA, magic links, password reset, and account management. Changelog excerpt: - Initial public release of the Authsome Dart SDK. - Typed client for sign-in, sign-up, sessions, MFA, magic links, password reset, email verification, and account management endpoints. - Request/response models generated from the Authsome OpenAPI contract.