♻ Refactor Python folder tree (#629)

Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

src/backend/app/tests_pre_start.py

@@ -3,7 +3,7 @@ import logging
 from sqlmodel import Session, select
 from tenacity import after_log, before_log, retry, stop_after_attempt, wait_fixed
 
-from app.db.engine import engine
+from app.core.db import engine
 
 logging.basicConfig(level=logging.INFO)
 logger = logging.getLogger(__name__)