Update views to use class-based views

Currently, most of the views use a [generic, class-based view](https://docs.djangoproject.com/en/6.0/topics/class-based-views/). but some of them do not. It would be nice to have consistency in this. Perhaps this can follow #544 

The non-class-based views are:
- `index`
- `privacy`
- `skill_profile`
- `account_overview`