[UX] Add redirect rule for 1.x pages that are now gone, otherwise all pages will yield 404

### Requirement

Context:

- #1050

It would be a better UX if the deleted page URLs were redirected, ideally to an explanation of what happened.

@yurishkuro - how about adding a banner/pageinfo at the top of https://www.jaegertracing.io/docs/1.76/ to explain that v1 reached EOL on Jan 1, 2026, and using that as a redirect target?

Review issue #1050 and the existing 1.x documentation URL, especially https://www.jaegertracing.io/docs/1.76/. Confirm which deleted 1.x URLs need redirects and whether the target should include a pageinfo or banner explaining the January 1, 2026 EOL; done means those URLs no longer return 404 and reach the explanation.

Written by the indexing model from the issue text.