Prepare a v09.docs.dnncommunity.org for the v9 archive

## Description of problem

In just a few weeks (Inshallah) DNN 10 will be out, and a lot of APIs will be cleaned up.

For some developers who are not deep into DNN, this will cause some confusion, as they will stumble upon APIs which don't exist any more.

## Description of solution

* [ ] My recommendation is to freeze the docs in the current state
* [ ] and republish on another domain - I would recommend `v09.docs.dnncommunity.org`
* [ ] then also adjust the theme to include information that this is an archive, and where to find the live docs

This would be a bit like https://v16.docs.2sxc.org/ - but I would recommend to make it better - so that you see it's an archive on every page.

The issue names no files, tests, or entry points. First review how the current DNNDocs site is built and published, then determine how to freeze the current documentation at v09.docs.dnncommunity.org and make the archive status and live-docs link visible on every page; done means the archived site is published and clearly labeled.

Written by the indexing model from the issue text.