Version 1 EOL followup

@chalin is already working on this.

Since Jan 13, 2026.

### Requirement

From https://github.com/jaegertracing/documentation/issues/1054#issuecomment-3735564712:

> [@yurishkuro](https://github.com/yurishkuro), after giving this more thought, I'd like to argue that the most appropriate action for end users is to:
>
> * Keep 1.76 pages indefinitely
> * Redirect 1.x pages to the corresponding 1.76 page, assuming it exists, or to the 1.76 landing page otherwise.
>
> Why?
>
> 1. **URLs are like public APIs.** There are lots of URLs to 1.x pages out there (blogs, runbooks, tickets, vendor docs, PDFs, bookmarks including OTel.io blog posts). Simply deleting them is a serious breaking change that just leaves clients **confused** and unaware of any suggested migration path.
> 2. By keeping 1.76 pages, **we can clearly mark v1 as EOL and funnel users to v2.** That is, add a banner to 1.76 pages + links to migration + 2.x equivalents so that users are informed, not surprised.
> 3. **Redirecting 1.x → latest 2.x silently changes semantics.** You propose redirecting to 2.x pages, but users following an old link expect 1.x behavior. Landing on 2.x can give wrong flags, configs, or deployment instructions — a correctness bug, not just UX.
> 4. **Keeping 1.76 pages has a _very low_ support burden.**

### Tasks

- [x] Redirect 1.x pages to corresponding 1.76 page if it exists, otherwise to the 1.76 landing page - #1056
- [ ] ...

As specified by @yurishkuro in #1054:

- [ ] Add banner to 1.76 pages. See Download page example below.
- [ ] Drop "latest) from "1.76 (latest)" since it's misleading

Reference, examples:

> on Download page we have a warning
>
>