I think that your admin or console web application should always go into its own project. This way you can have more control if ever it is to be deployed to an intranet setting, if you need to hide certain functionality from your main site, etc. Co-mingling these two concerns under one site rarely ends up being a good idea as the site grows and grows. Also, an admin site rarely benefits from the design and so on of the main application. Administrative functions usually benefit from a more direct layout, additional screens, more security, etc.
Think about http://console.sitename.com/forum/index. This is much clearer and can still have ties to your forum application. The concerns are very much separated here.