Implement Content Signals by default (and document) on shipped robots.txt, both pure vanilla and Anubis

[DiegoPino]

See

• https://contentsignals.org
• https://blog.cloudflare.com/content-signals-policy/?utm_source=chatgpt.com/

Also, make sure we are also not only sending noAI but also noImageAI via X-Robots-tags (as a config/environmental option through docker for ngnix) in cantaloupe responses and probably our meta headers in HTML (But that is a different issue we have somewhere else?)

I would love to be able to send Content-Signals headers, but those are not a standard yet

Also, Draft but I hope it becomes a standard

https://www.ietf.org/archive/id/draft-it-aipref-attachment-00.html#name-introduction
https://datatracker.ietf.org/doc/html/draft-ietf-aipref-vocab-04