added Account Linking/fixed Hackclub auth (again)

So now its getting rememberd if you also have a password and not only auth with google or hackclub.
Also in the database there is a completly new columm for the hackclub ID.

Backend:hackclub_callback() now also checks for Login/register or Link Modus.
google_login() now accepts link mode.There are two new routes for unlinking google and hackclub.
And last but not least. There is also a secruity check. The last used login methoid cant be deleted.