Create admin page - Frontend

- [ ] Section that allows to add user by username + create password (POST request to api/people/new)
- [ ] Section that allows to delete user by username (DELETE request to api/people query parms: id)
- [ ] Section that allows to reset password by username (PUT request to api/people/reset query params: id)
- [ ] Section that allows to change user role between admin and staff (PUT request api/people/role)
- [ ] Link to navbar
- [ ] Restrict access to users with admin privileges
- [ ] Toast if error

Start by finding the frontend route and navbar entry point, then inspect existing calls to api/people/new, api/people, api/people/reset, and api/people/role. Check how admin privileges and error toasts are handled elsewhere. Done means all listed user-management sections work, the link is available, non-admin access is restricted, and errors show a toast.

Written by the indexing model from the issue text.