[FEATURE] First-run / About enrichment — changelog deep link & release notes UX

[krwg]

Summary

Extend existing About surfaces with changelog anchor (same GitHub Releases), SPDX / license succinct line, contributor CTA parity.

Background

Reduces support duplicates asking “what changed”.

Scope

• Derived version string already centralized — unify display in splash optional.
• Secondary link CHANGELOG.md or tagged compare view.
• Localized tooltip strings verifying external navigation uses hardened openExternal path.

Acceptance criteria

• Links open externally with single user gesture.
• Broken network does not crash UI (guard fetch if later inline notes added).
• Mirrors EN/RU i18n keys.

Technical notes

If inline release notes fetched later — sign or pin commit hash.

Definition of done

Copy review with maintainer persona under 120s onboarding path video script optional.