### Summary

A pass-through endpoint supplied as a raw dictionary is unauthenticated when the `auth` field is omitted, even though the Pydantic `PassThroughGenericEndpoint.auth` field defaults to `True`

### Current behavior

`_register_pass_through_endpoint()` accepts either a `PassThroughGenericEndpoint` or a raw dictionary

For a Pydantic object, `model_dump()` materializes the default `auth=True`. For a raw dictionary, the registration code uses the dictionary directly:

~~~python if isinstance(endpoint, PassThroughGenericEndpoint): endpoint_data = endpoint.model_dump() else: endpoint_data = endpoint

auth = endpoint_data.get("auth") auth_enforced = auth is not None and str(auth).lower() == "true" dependencies = [Depends(user_api_key_auth)] if auth_enforced else None ~~~

Therefore `auth` omitted from a raw config becomes `None`, `auth_enforced` becomes `False`, and the generated route has no LiteLLM authentication dependency. The registration comment says unauthenticated forwarding should require explicit opt-in, but the predicate implements the opposite for raw dictionaries

### Reproduction

Define a pass-through endpoint in a source that supplies dictionaries, such …