Publish Trajectory demo on GitHub Pages

[Dmitryaf]

What changed

• deploy the validated demo build to GitHub Pages after CI succeeds on main
• use a /trajectory/ build base and hash routes compatible with static hosting
• scope PWA assets, manifest, and navigation fallback to the Pages path
• add the live demo link and its synthetic local-data boundary to the README

Why

The public repository currently shows screenshots and source code but has no working product link. This publishes the existing synthetic-data showcase without exposing production authentication, cloud synchronization, or private data.

Checks

• npm.cmd run check — 21 tests passed, build passed
• npm.cmd run test:e2e — 3 Playwright scenarios passed
• Pages-specific build with GITHUB_PAGES=true
• local HTTP smoke: index, manifest, demo JSON, and built JS asset returned 200 under /trajectory/

[Dmitryaf]

Published the already reviewed commit 1d666be to main with a non-forced REST fast-forward because GitHub merge operations repeatedly returned 502 / remained stuck. The main push CI and GitHub Pages deployment both passed, and the live site was smoke-tested.