switch to dataclass, cleanup

app/models/user.py

@@ -1,11 +1,12 @@
+from dataclasses import dataclass
 from typing import Optional
 from app.db import get_db
 from flask_login import UserMixin
 
+@dataclass
 class User(UserMixin):
-    def __init__(self, id: int, username: str ):
-        self.id: int = id
-        self.username: str = username
+    id: int
+    username: str
 
     @staticmethod
     def get(user_id: int | str) -> Optional["User"]: