SEO audit - best pages by link

[mnelsonBT]

Adding the "best by pages" links to homepage that were not already added in PRs #17570 and #17578

Description

Adds an internal homepage link to the first meaningful mention of "Ethereum" on each of the site's highest-traffic content pages (that were not yet addressed by above PRs).

For markdown pages:

• Skipped YAML frontmatter, headings, and already-linked mentions
• Only the first standalone "Ethereum" in body paragraph text is linked per page

For pages driven by next-intl translation JSON:

• First qualifying body-content mention linked using the appropriate rendering pattern
  -- HTML <a href="/"> added to JSON
• TSX adjusted as necessary to add links
  --plain t() calls swapped to <Translation> component (or a: mapping added to t.rich()
  for what-is-ethereum)
  -- <Translation> component uses htmr to parse <a href="/">Ethereum</a> in JSON values

[netlify]

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[wackerow]

Lgtm.. can handle non-English changes separately