fix(endpoint): import ModelEndpoint from core database

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>

src/endpoint_resolver.py

@@ -11,7 +11,7 @@ import subprocess
 from typing import Optional, Tuple, Dict
 from urllib.parse import urlparse, urlunparse
 
-from src.database import SessionLocal, ModelEndpoint
+from core.database import SessionLocal, ModelEndpoint
 from src.llm_core import _detect_provider, _host_match
 
 logger = logging.getLogger(__name__)
@@ -285,6 +285,8 @@ def resolve_endpoint(
         # If no (usable) model specified, pick the first enabled chat model.
         if not model:
             model = _first_chat_model(_endpoint_enabled_models(ep)) or ""
+        if not model and not fallback_model:
+            logger.warning('[resolve_endpoint] no usable model (all models hidden or list empty)')
 
         return chat_url, model or fallback_model, headers
     except Exception as e:

tests/test_auth_regressions.py

@@ -81,13 +81,13 @@ def _auth_regressions_stubs(monkeypatch):
         resolve_endpoint=MagicMock(return_value=("", "", {})),
         normalize_base=MagicMock(),
         build_chat_url=MagicMock(),
+        build_models_url=MagicMock(),
         build_headers=MagicMock(),
     )
     monkeypatch.setitem(sys.modules, "core.database", db)
     monkeypatch.setitem(sys.modules, "core.auth", auth)
     monkeypatch.setitem(sys.modules, "src.endpoint_resolver", ep)
 
-
 from fastapi import HTTPException
 
 # ---------------------------------------------------------------------------