Optimise /odoo-ia/ and fix the site-wide 'null' header bug

/odoo-ia/ (279 impressions at position 6.8 for 'odo ia', zero clicks):
- H1 answers the query instead of describing the page: 'Odoo IA: que hace la
  inteligencia artificial en Odoo (y que no)'.
- Hero stats '60+ Recursos / 85% Automatizacion / 24/7 Operacion' replaced with
  the three honest routes: nativo / integracion / fuera. '85%' had no source.
- 'Empieza por aqui': five curated entry points, so the hub is a guide and not
  only a list of 55 links.
- Hosting CTA with utm_medium=hub-cta and a disclosure.
- FAQ (5 questions) + matching FAQPage schema. Answers are conditional on
  version and edition; no feature list is asserted, because odoo.com has no AI
  page to verify one against.

Separately, a real defect found while checking the render: 1,714 script blocks
across 840 pages called document.write(null) or set innerHTML = null, so the
header and footer rendered the literal text 'null'. Replaced with
createHeader()/createFooter(), which restores the real navigation on every
affected page.

pt/odoo-hosting/index.html

@@ -230,11 +230,8 @@
 <body>
     <!-- Header -->
     <script src="/components/header.min.js"></script>
-    <script>
-        document.write(/*W6-static*/null);
-    </script>
-
-    <main role="main">
+    <script>document.write(createHeader());</script>
+<main role="main">
     <!-- Breadcrumb Navigation -->
     <nav class="breadcrumb-nav" style="background: #2a2a2a; padding: 1rem 0; border-bottom: 1px solid rgba(255,107,53,0.2);">
         <div class="container">
@@ -519,11 +516,8 @@
 
     <!-- Footer -->
     <script src="/components/footer.min.js"></script>
-    <script>
-        document.write(/*W6-static*/null);
-    </script>
-
-    <!-- Cookie Banner -->
+    <script>document.write(createFooter());</script>
+<!-- Cookie Banner -->
     <script src="/js/cookie-banner.min.js"></script>
 
     <!-- Directory Card Fix Script -->