fix(web): SEO fixes from Search Console and Lighthouse audit (#1039)

* fix(web): SEO fixes from Search Console and Lighthouse audit

Technical:
- Emit BreadcrumbList JSON-LD from the same trail as the visual breadcrumbs
  on every SeoSubpageShell page.
- absoluteUrl() no longer appends a trailing slash to file paths. The
  Organization and publisher logo URLs pointed at /vocalinux.png/, a 404.
- Fetch the GitHub star count once at build time in next.config.js and
  drop the client-side api.github.com fetch and preconnect (Lighthouse
  "third-party code" on every page). Falls back to the "GitHub" label.
- Fix h1 -> h3 heading skips on 11 pages by promoting the leading card
  headings to h2; new .subpage-card-title keeps the old h3 sizing.
- Header and footer logo get alt="" next to the visible "Vocalinux" text.
- Footer links every guide, distro and feature page, so the pages added in
  #1038 and /vs-nerd-dictation/ (Discovered, not indexed) and /writers/
  (no inbound links) are linked sitewide.

Titles and descriptions:
- Rewrite titles/descriptions for pages with high impressions and low CTR
  in Search Console (home, FAQ, compare, languages, open-source, GPU,
  alternatives, offline, install) to lead with the queries they rank for.
- Distro pages use "<Distro> Speech to Text: Offline Voice Typing Setup"
  as the search title; the on-page h1 is unchanged.
- Remove brand repetition and shorten 75+ character titles.
- Bump sitemap lastmod for the rewritten pages.

* fix(web): keep home install card titles styled

The home page's install cards still use h3; only /install/ moved to h2.
Style both so the home cards keep their size and spacing.

.github/workflows/unified-pipeline.yml

@@ -576,6 +576,9 @@ jobs:
 
       - name: Install and build
         working-directory: ./web
+        env:
+          # next.config.js reads the repo star count at build time
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         run: |
           npm ci || npm install
           npm run deploy