ModelEndpoint is defined in core.database, not src.database. The wrong
import silently prevented the module from loading in deployment
configurations that do not have a src/database.py shim, resulting in an
ImportError at startup.
Also adds a warning log when resolve_endpoint finds no usable model
(all models hidden or the list is empty), making the otherwise-silent
failure visible in operator logs.
The test_auth_regressions stub for src.endpoint_resolver was missing the
build_models_url attribute, which caused test collection errors.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
