I want to create a internal forum for members from another website. The idea is that i want to create accounts for certain people and i do not want people to be able to create these accounts on theyr own. Is there any way to disable the registration buttons and page so accounts can only be created from the control panel?

You can edit the register route to remove the page and remove the register link from the template.

But, instead of this why not integrate the register/login of the other website into codoforum ?
You won't have to create an account for each one of them this way.

Because users do not register on the other website. They don't register at all. We make the accounts for them to use. Anyway, i disabled every register link and the page itself. Thank you