catch_exception crashes when request.state.tenant_id is unset

[juangalt]

keep/api/api.py catch_exception formats request.state.trace_id and request.state.tenant_id while handling an exception. Starlette State.__getattr__ raises AttributeError when either attribute is absent, so the handler fails and the original exception is discarded.

The same body is on v0.53.0 and current main. Fix: getattr for both attributes and logger.exception, keeping the JSON 500 shape {message, trace_id, error_msg}.

PR: #6854

This is not #6089 or #6100; those are different tenantId surfaces.