refactor: improve code formatting and organization across multiple files

backend/app/api/auth.py

@@ -25,17 +25,25 @@ async def login(credentials: LoginRequest) -> AuthResponse:
     return issue_token_for_user(user)
 
 
-@router.post("/register", response_model=AuthResponse, status_code=status.HTTP_201_CREATED)
+@router.post(
+    "/register", response_model=AuthResponse, status_code=status.HTTP_201_CREATED
+)
 async def register(payload: RegisterRequest) -> AuthResponse:
     try:
         user = register_user(payload.username, payload.password, payload.full_name)
     except ValueError as exc:
         message = str(exc)
-        status_code = status.HTTP_409_CONFLICT if "exists" in message else status.HTTP_400_BAD_REQUEST
+        status_code = (
+            status.HTTP_409_CONFLICT
+            if "exists" in message
+            else status.HTTP_400_BAD_REQUEST
+        )
         raise HTTPException(status_code=status_code, detail=message) from exc
     return issue_token_for_user(user)
 
 
 @router.get("/me", response_model=UserPublic)
-async def read_current_user(current_user: UserPublic = Depends(get_current_user)) -> UserPublic:
+async def read_current_user(
+    current_user: UserPublic = Depends(get_current_user),
+) -> UserPublic:
     return current_user