Blog into docs

[obrasier]

Have ported the blog changes into the DOCS site - I couldn't get the blog site to host the docs properly, so I decided to port them the other way.

Things missing:

• Sam's review
• screenshot of relevance demo
• some images in blogs/case studies
• dashboard.gumnut.dev < still links there, this is down
• less background patterns right now, I'll add more soon
• deleting blog/ folder and simplifying it to be just one "site" - still haven't deleted the old stuff yet in case there's anything I need to copy over.

All of these can be added post-merge.