[jacquard] migrate Vec<Scope<S>> to Scopes<S> container
- Replace all Vec<Scope<S>> fields with Scopes<S> across jacquard-oauth
- Migrate OAuthState/OAuthSession persistence format (Vec<String> → String)
- Migrate main crate consumers and integration tests
- Retire old utility methods (parse_multiple, serialize_multiple, remove_scope)
- Use expect instead of unwrap_or_default for scope parsing in token refresh