get_available_models() references 'logger' in the except block of
the custom endpoint fetch (added in PR #18), but 'logger' is never
imported or defined in api/config.py. When the custom endpoint is
unreachable (the normal case -- most users don't have a local LLM),
the except handler raises NameError: name 'logger' is not defined,
which propagates as a 500 on every GET /api/models request.
This broke 7 test_sprint11 tests and caused the model dropdown to
fail for all users regardless of whether they have a custom endpoint.
Fix: replace logger.debug() with a silent pass -- the exception is
expected when no local LLM is configured and needs no logging.
Tests: 237 passed, 0 failed.