fix(marketing): RFC 9309 robots.txt semantics + lazy marketing import

- Remove redundant named User-agent blocks (Googlebot, Bingbot, ClaudeBot,
  GPTBot, PerplexityBot, Applebot) that per RFC 9309 §2.2 overrode the
  wildcard and granted those bots access to /api/, /admin, /account.
- Add explicit Google-Extended and ChatGPT-User blocks (AI opt-in
  signaling) with full Allow/Disallow rule sets.
- Fix /blog → /blog/ for prefix-match consistency.
- Move src.marketing.routes import inside recordings.index() function
  to localize cross-blueprint dependency (was at module top, inverting
  initialization order).
- Add shadow-warning comment at marketing_bp registration site.

static/robots.txt

@@ -12,7 +12,7 @@ Allow: /tarifs
 Allow: /fonctionnalites
 Allow: /conformite
 Allow: /contact
-Allow: /blog
+Allow: /blog/
 Allow: /legal/
 Disallow: /api/
 Disallow: /admin
@@ -26,23 +26,46 @@ Disallow: /oublie
 Disallow: /verifier-email
 Disallow: /webhooks/
 
-# Search/AI crawlers explicitly allowed on public marketing surface
-User-agent: Googlebot
+# Google-Extended (Bard/Gemini training): explicit opt-in to public marketing
+User-agent: Google-Extended
 Allow: /
+Allow: /tarifs
+Allow: /fonctionnalites
+Allow: /conformite
+Allow: /contact
+Allow: /blog/
+Allow: /legal/
+Disallow: /api/
+Disallow: /admin
+Disallow: /account
+Disallow: /share/
+Disallow: /app/
+Disallow: /checkout
+Disallow: /login
+Disallow: /signup
+Disallow: /oublie
+Disallow: /verifier-email
+Disallow: /webhooks/
 
-User-agent: Bingbot
-Allow: /
-
-User-agent: ClaudeBot
-Allow: /
-
-User-agent: GPTBot
-Allow: /
-
-User-agent: PerplexityBot
-Allow: /
-
-User-agent: Applebot
+# ChatGPT-User (on-demand browsing): explicit opt-in to public marketing
+User-agent: ChatGPT-User
 Allow: /
+Allow: /tarifs
+Allow: /fonctionnalites
+Allow: /conformite
+Allow: /contact
+Allow: /blog/
+Allow: /legal/
+Disallow: /api/
+Disallow: /admin
+Disallow: /account
+Disallow: /share/
+Disallow: /app/
+Disallow: /checkout
+Disallow: /login
+Disallow: /signup
+Disallow: /oublie
+Disallow: /verifier-email
+Disallow: /webhooks/
 
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