refactor: improve code formatting and organization across multiple files

backend/app/repositories/trains.py

@@ -1,12 +1,13 @@
 from __future__ import annotations
 
-import sqlalchemy as sa
 from uuid import UUID
+
+import sqlalchemy as sa
 from sqlalchemy.orm import Session
 
 from backend.app.db.models import Train
-from backend.app.repositories.base import BaseRepository
 from backend.app.models import TrainCreate
+from backend.app.repositories.base import BaseRepository
 
 
 class TrainRepository(BaseRepository[Train]):