Refactor to manager-centric model, add team calendar for all users

Key changes:
- Removed office-centric model (deleted offices.py, office-rules)
- Renamed to team-rules, managers are part of their own team
- Team calendar visible to all (read-only for employees)
- Admins can have a manager assigned

services/auth.py

@@ -61,14 +61,14 @@ def authenticate_user(db: Session, email: str, password: str) -> User | None:
     return user
 
 
-def create_user(db: Session, email: str, password: str, name: str, office_id: str = None, role: str = "employee") -> User:
+def create_user(db: Session, email: str, password: str, name: str, manager_id: str = None, role: str = "employee") -> User:
     """Create a new user"""
     user = User(
         id=str(uuid.uuid4()),
         email=email,
         password_hash=hash_password(password),
         name=name,
-        office_id=office_id,
+        manager_id=manager_id,
         role=role,
         created_at=datetime.utcnow().isoformat(),
         updated_at=datetime.utcnow().isoformat()