fix(seo): canonical self-deindexing on /docs/*, truthful llms.txt, real sitemap dates, RSS feed, breadcrumbs, per-article OG images

- /docs subpages canonicalized to /docs and had no descriptions; each now
  uses pageMetadata with its own path (was: Google could index at most one)
- llms.txt claimed Team EUR 149, RBAC/SLA and BYO-cloud that do not exist;
  regenerated from lib/seo.ts truth + new llms-full.txt with docs content
- sitemap stamped lastModified=now on every request; now real per-route dates
  from new lib/articles.ts registry (single source for guides index/sitemap/RSS)
- new /feed.xml RSS 2.0 route + alternates link in root layout
- articleJsonLd: image (per-guide opengraph-image via lib/og-article.tsx),
  Person author, wordCount; new breadcrumbJsonLd on guides + docs
- GSC verification via NEXT_PUBLIC_GSC_VERIFICATION (documented in .env.example)
- dropped fabricated Enterprise EUR 499 offer from SoftwareApplication JSON-LD
- article-shell: OL/Table/Note primitives for upcoming articles

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SXUwmPVRTD8AKQtio6gCN5

.env.example

@@ -13,6 +13,9 @@ BETTER_AUTH_SECRET=replace-me-with-32-bytes-of-random-hex-1234567890abcdef
 BETTER_AUTH_URL=http://localhost:3001
 NEXT_PUBLIC_APP_URL=http://localhost:3001
 NEXT_PUBLIC_API_URL=http://localhost:4000
+# Google Search Console HTML-tag verification token (content attribute only).
+# Leave empty in dev; set in production, then submit /sitemap.xml in GSC.
+NEXT_PUBLIC_GSC_VERIFICATION=
 
 # ---- GitHub OAuth ("Continue with GitHub") ----
 # Create at https://github.com/settings/applications/new