v0.16.1 — Documentation patch: CHANGELOG links in the long and five short READMEs

Documentation patch. Two additive changes that close a documentation gap
left by v0.16.0 — no behaviour change, no API drift, no compat impact.

Added

• CHANGELOG.md linked from the version section of README.md and
  README.de.md, so a reader of either long README finds the project-wide
  change log and the GitHub release notes without leaving the document
  (#70).
• Same paragraph added to the five short READMEs (zh, es, fr, ja,
  pt), so a reader in any shipped language lands on the same hint
  (#71).

Not included (consciously)

• No content change in the short READMEs beyond the new paragraph; the
  Changelog topic was deliberately not introduced into them, only linked
  where their existing structure already mentions version history.
• Wiki does not adopt the link — the Changelog topic does not exist there
  and there is nothing to point at.
• AGENTS.md and CLAUDE.md untouched, so the byte-identity check in CI
  keeps matching the previous release.

Contained issues: OPEN-110, OPEN-112.