Hydra Auth Redirect

Redirect the browser to Hydra's actual /oauth2/auth endpoint.

Unlike the other OAuth2 endpoints which we proxy server-side, the auth endpoint MUST be a browser redirect because Hydra sets session cookies during the authorization flow. If we proxy it, the cookies land on our domain (localhost:8000) but Hydra's subsequent redirects go to its own domain (localhost:4444), losing the cookies and breaking the flow.