Prevents environment variable leaking between tests. All DATA_DIR, JWT_SECRET_KEY, and SCRIPT_TIMEOUT assignments in fixtures now use monkeypatch.setenv() which auto-reverts after each test. Removes manual os.environ.pop() cleanup lines.
- JWT auth with role-based access control (viewer/analyst/admin/km_admin) - Endpoints: health, sync manifest, data download, query, users CRUD, corporate memory, session/artifact upload - 18 API tests covering auth, RBAC, all endpoints