refactor: replace SQLModel with QueryModel in various models and update query methods

backend/app/models/activity_events.py

@@ -3,12 +3,13 @@ from __future__ import annotations
 from datetime import datetime
 from uuid import UUID, uuid4
 
-from sqlmodel import Field, SQLModel
+from sqlmodel import Field
 
 from app.core.time import utcnow
+from app.models.base import QueryModel
 
 
-class ActivityEvent(SQLModel, table=True):
+class ActivityEvent(QueryModel, table=True):
     __tablename__ = "activity_events"
 
     id: UUID = Field(default_factory=uuid4, primary_key=True)