BetterAuth defaulted basePath to /api/auth but NestJS controller routes
to /auth/* (no global prefix). The auth client also pointed at the web
frontend origin instead of the API server, and LoginButton used a
nonexistent GET /auth/signin/authentik endpoint.
- Set basePath: "/auth" in BetterAuth server config
- Point auth client baseURL to API_BASE_URL with matching basePath
- Add genericOAuthClient plugin to auth client
- Use signIn.oauth2({ providerId: "authentik" }) in LoginButton
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>