chore: retire demo technical debt

backend/app/api/reading_events.py

@@ -4,7 +4,7 @@ from datetime import datetime, timezone
 from typing import Literal
 
 from fastapi import APIRouter, Depends, HTTPException, status
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, ConfigDict, Field
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -34,6 +34,8 @@ class ReadingEventCreate(BaseModel):
 class ReadingEventResponse(BaseModel):
     """Reading event response."""
 
+    model_config = ConfigDict(from_attributes=True)
+
     id: int
     child_profile_id: str
     story_id: int | None
@@ -41,9 +43,6 @@ class ReadingEventResponse(BaseModel):
     reading_time: int
     created_at: datetime
 
-    class Config:
-        from_attributes = True
-
 
 @router.post(
     "/reading-events",