3cb4d01073
- auth.py: _create_access_token had no jti claim, so two refreshes within the same wall-clock second produced byte-identical access tokens (same failure mode already fixed for refresh tokens earlier) - test_refresh_endpoint.py: usernames (jwttoken, refreshuser, etc.) collided with test_auth_endpoints.py's own test usernames once run in the same pytest session against a shared DB with no per-test isolation -- exactly how run_checkpoint_tests.py invokes pytest. Namespaced this file's usernames with a refep_ prefix. Full backend suite (63 tests) passes clean end-to-end against a real Postgres with real migrations applied.