Fix and re-add podcasts to frontend

[eikhr]

Podcasts did not work in frontend because of problems with the Soundcloud API. All frontend code for podcasts is removed in webkom/lego-webapp#3158, so this will have to be reverted and fixed.

It would be cool to have the podcast page and components working again.

the fix is to register an application with soundcloud, provide the details to the backend, and create and return the token (as per soundcloud API flow) with the podcasts API in LEGO.
webkom/lego-webapp#3158 (comment)