chore: point the licence and the security policy at FerroHEALTH/FerroSMART

[rubentalstra]

What changed and why

FerroSMART moved to the FerroHEALTH organisation on 2026-10-01. The Licensed Work line in LICENSE and the advisory link in SECURITY.md now name https://github.com/FerroHEALTH/FerroSMART in place of the old address under rubentalstra/. The maintainer handle in MAINTAINERS.md is a person and stays. git grep -n 'rubentalstra/' now finds nothing.

Closes #7

Licensing of contributions

• I accept the terms in CONTRIBUTING.md § Licensing of contributions: I have the right to submit this work, I license it under the project licence of the version it lands in, and I grant the Licensor the relicensing right stated there.

Checklist

• Shell and workflow files are clean: shellcheck --severity=style, actionlint, zizmor --min-severity=low .github/.
• Rust gates pass, once a workspace exists: no workspace yet.
• Docs are updated, if behaviour changed.
• Every commit is signed.
• No AI or assistant attribution anywhere in the commits or this PR.