refactor: improve code formatting and organization across multiple files

backend/app/core/config.py

@@ -1,11 +1,9 @@
 from functools import lru_cache
+from typing import Optional
 
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
-from typing import Optional
-
-
 class Settings(BaseSettings):
     project_name: str = "Rail Game API"
     version: str = "0.1.0"

backend/app/core/security.py

@@ -25,12 +25,18 @@ def create_access_token(subject: str, expires_delta: timedelta | None = None) ->
         expires_delta or timedelta(minutes=settings.access_token_expire_minutes)
     )
     to_encode: Dict[str, Any] = {"sub": subject, "exp": expire}
-    return jwt.encode(to_encode, settings.jwt_secret_key, algorithm=settings.jwt_algorithm)
+    return jwt.encode(
+        to_encode, settings.jwt_secret_key, algorithm=settings.jwt_algorithm
+    )
 
 
 def decode_access_token(token: str) -> Dict[str, Any]:
     settings = get_settings()
     try:
-        return jwt.decode(token, settings.jwt_secret_key, algorithms=[settings.jwt_algorithm])
-    except JWTError as exc:  # pragma: no cover - specific error mapping handled by caller
+        return jwt.decode(
+            token, settings.jwt_secret_key, algorithms=[settings.jwt_algorithm]
+        )
+    except (
+        JWTError
+    ) as exc:  # pragma: no cover - specific error mapping handled by caller
         raise ValueError("Invalid token") from exc