fix(tests): add missing getAccessTokenClaims mock and update OIDC scope assertion

Summary

• Add getAccessTokenClaims to keycloakAuthService mock in authStore.test.js and store/modules/auth.test.js
• Update oidcConfig.test.js scope assertion to include roles (matches oidcConfig.js)
• Use mockImplementationOnce to prevent mock return value leaking between tests

Context

mapOidcUserToState() in auth.js calls keycloakAuthService.getAccessTokenClaims() to extract realm_access.roles from the access token. The mock was missing this method, causing initialize() to throw before registerSilentRenewCallback() was reached, which made logout cleanup tests fail.

All 166 frontend tests pass.