When deleting a user via CLI (`vikunja user delete <id> -n`), the user
row was deleted first, then `notifications.Notify` was called. But
`Notify` calls `User.ShouldNotify()` which queries the database to check
the user's status — and since the row was already deleted within the same
transaction, it returned `ErrUserDoesNotExist`.
Move the notification call before the `DELETE` so the user row still
exists when `ShouldNotify` checks it.
Closesgo-vikunja/vikunja#2335