♻ Refactor Python folder tree (#629)

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

src/backend/app/tests/conftest.py

@@ -5,8 +5,7 @@ from fastapi.testclient import TestClient
 from sqlmodel import Session, delete
 
 from app.core.config import settings
-from app.db.engine import engine
-from app.db.init_db import init_db
+from app.core.db import engine, init_db
 from app.main import app
 from app.models import Item, User
 from app.tests.utils.user import authentication_token_from_email