Add landing page at nest-native.dev/reference-app

[rodrigobnogueira]

Summary

• Make https://nest-native.dev/reference-app/ resolve, the same way /nest-drizzle-native/ and /nest-trpc-native/ already do, by enabling GitHub Pages on this repo.
• Ship a styled landing page (mirroring the org landing's visual language) and rendered architecture doc as the Pages content.
• Drop the now-stale nest-trpc-handover.md archival file.

Changes

• docs/index.html — landing page. Hero with tagline + GitHub CTA + architecture-doc CTA + a "stack at a glance" panel. "What it is" section restating the reference-vs-product boundary. Eight-milestone status grid (all done). Link-out section to source, architecture, getting started, CHANGELOG, v0.1.0 release, both library doc sites.
• docs/styles.css — copied from nest-native/nest-native.github.io and extended with .milestones / .links-list blocks for the two new sections. Same dark theme, same radial gradients, same accent/teal palette so the page feels native next to the other org pages.
• docs/_config.yml — minimal Jekyll config (baseurl: /reference-app, no theme, excludes top-level project metadata files from publishing).
• docs/architecture.md — in-repo relative links (](../src/…)) rewritten to absolute https://github.com/nest-native/reference-app/blob/main/… URLs so the doc renders correctly both from nest-native.dev/reference-app/architecture.html and from the GitHub blob view.
• Removed nest-trpc-handover.md — its content (root cause + TDD plan for the missing-await bug in nest-trpc-native) was archival; the fix shipped in 0.4.3 and the repo is on it.

Modules Touched

• Tooling / CI / docs only

Public Surface (libraries)

• No use of library internals introduced.

Security Review

• Static HTML/CSS only — no scripts, no forms, no user input. No XSS surface.
• All outbound links are explicit URLs (no javascript:, no inline event handlers).
• No new dependencies — Jekyll/kramdown run server-side on GitHub Pages and are not part of this repo's lockfile.
• No secrets in markup or comments.
• No unresolved high-risk security finding remains.

Dependency Review

• No dependency or lockfile changes.

Migrations

• No schema changes.

Validation

• npm run ci — passes locally (45/45 tests, 91.43% statements / 95.55% functions). The docs path is not exercised by CI but adding nothing to the JS path shouldn't affect it.
• Manually verified docs/architecture.md no longer contains any ](../ relative links: grep -oE '\]\(\.\./' returns empty.
• Live Pages render — can only verify after Pages is enabled (post-merge step below).

Validation Notes

• The Jekyll build runs server-side on GitHub Pages. Locally building it would require installing the github-pages Ruby gem, which is heavier than the change warrants. If the server build fails on push, Actions will surface it.

Pages enablement (one-time, post-merge)

After this PR merges, run once:

gh api -X POST repos/nest-native/reference-app/pages \
  -f source[branch]=main -f source[path]=/docs

The verified custom domain on nest-native.github.io auto-routes
nest-native.dev/<repo>/ to each Pages-enabled repo, so no CNAME
file is required here. After ~1 minute,
https://nest-native.dev/reference-app/ should serve the new landing page.

Release Notes

• Release impact: CHANGELOG.md updated under [Unreleased] with this landing-page section + the one-time Pages-enablement note.