chore(backend): add black/isort/flake8 + pre-commit

backend/app/models/__init__.py

@@ -1,5 +1,5 @@
 from app.models.activity import Activity
-from app.models.org import Department, Team, Employee
+from app.models.org import Department, Employee, Team
 from app.models.projects import Project, ProjectMember
 from app.models.work import Task, TaskComment
 

backend/app/models/org.py

@@ -1,7 +1,5 @@
 from __future__ import annotations
 
-from typing import Optional
-
 from sqlmodel import Field, SQLModel