refactor: improve code formatting and organization across multiple files

backend/app/services/auth.py

@@ -43,7 +43,9 @@ def to_public_user(user: UserInDB) -> UserPublic:
     return UserPublic(username=user.username, full_name=user.full_name)
 
 
-def register_user(username: str, password: str, full_name: Optional[str] = None) -> UserInDB:
+def register_user(
+    username: str, password: str, full_name: Optional[str] = None
+) -> UserInDB:
     normalized_username = username.strip()
     if not normalized_username:
         raise ValueError("Username must not be empty")

backend/app/services/network.py

@@ -6,13 +6,14 @@ from typing import Iterable, cast
 
 from geoalchemy2.elements import WKBElement, WKTElement
 from geoalchemy2.shape import to_shape
+
 try:  # pragma: no cover - optional dependency guard
     from shapely.geometry import Point  # type: ignore
 except ImportError:  # pragma: no cover - allow running without shapely at import time
     Point = None  # type: ignore[assignment]
 
-from sqlalchemy.orm import Session
 from sqlalchemy.exc import SQLAlchemyError
+from sqlalchemy.orm import Session
 
 from backend.app.models import StationModel, TrackModel, TrainModel
 from backend.app.repositories import StationRepository, TrackRepository, TrainRepository