[KeyffMS]

Addresses #99.

Implements the repository-hosted SightAdapt product website from the content contract in #124 and the immutable release in #98.

Key points:

• dependency-free static HTML/CSS/JS;
• canonical production URL remains https://aiteracja.pl/sightadapt/;
• GitHub Pages fallback builds for /SightAdapt/ from the same source;
• complete Home, Features, Download, Documentation, How it works, FAQ, Releases, Privacy, Legal, Security and Support surfaces;
• canonical brand SVGs are copied from repository assets at build time;
• current immutable release metadata, direct GitHub Release download, SHA-256, SBOM and compliance links;
• no cookies, analytics, remote fonts, advertising or third-party embeds;
• skip navigation, semantic landmarks, visible focus, meaningful alt text, reduced-motion handling and keyboard-accessible mobile navigation;
• dependency-free Python build and validation scripts;
• CI validates both /SightAdapt/ and /sightadapt/ builds before a main-branch Pages deployment.

This PR intentionally does not claim #99 complete until the default branch protection requirement and live GitHub Pages deployment are verified.