docs: add KyaniteLabs cross-link footer (SEO/internal linking)

[simongonzalezdc]

Why

Internal linking strengthens SEO/GEO authority flow between KyaniteLabs projects and surfaces related open-source tools to readers. Additive and low-maintenance.

What changed

• Added a consistent Part of KyaniteLabs footer to README.md linking to 3 related projects + kyanitelabs.tech.
• Docs only — no code, dependencies, or behavior change.

Verification

• Footer diff rendered; all links resolve to valid repos and the live site.
• License-accurate wording (neutral "More from KyaniteLabs", since some repos are BSL/source-available, not open-source).
• CI green.

Maintainer checklist

• Docs-only change
• No code/behavior change
• Links + license wording verified