feat(seo): wire internal links between the 17 blog posts and the pages that sell

The blog was an island: zero post→page links to hosting/upgrade/support/courses,
and only one page→post link in the whole site. Posts ranked for nothing while the
old blog host ranked for our long-tail queries.

Posts → pages (26 new in-body contextual links across 17 posts):
each post now carries one or two links to the page that answers its reader's next
question — odoo-hosting-2027, odoo-community-upgrade, support, the workshops hub,
the n8n masterclass, and the plan pricing on index.html#pricing.

Pages → posts (7 pages, one contextual link each):
index.html (OCA section), odoo-hosting-2027, odoo-community-upgrade, support,
workshops/, odoo-n8n-masterclass/, odoo-erp-automation-bootcamp/ now link into the
post that fits their own subject. The clearest miss is fixed — the
community-vs-enterprise-cost post and the odoo-community-upgrade page now link
to each other.

Anchors wrap existing sentences where the text already said the thing; four short
linking sentences were added (index OCA section, support first-steps FAQ, masterclass
lessons, bootcamp included section). No new components, no related-posts widget,
in-body anchors only. English pages only; DE/ES untouched (translator follow-up).

blog/posts/odoocommunity-agents.html

@@ -261,7 +261,7 @@
                         build agentic workflows.
                     </p>
                     <p>
-                        Combined with N8N automation workflows and custom
+                        Combined with <a href="../../odoo-n8n-masterclass/">N8N automation workflows</a> and custom
                         modules hosted on ODOO4projects, you can create
                         sophisticated pipelines where AI agents coordinate
                         across multiple ODOO apps, external services, and
@@ -271,7 +271,7 @@
                     <h2>Why Host with ODOO4projects?</h2>
                     <p>
                         Running AI agents alongside ODOO requires reliable,
-                        scalable infrastructure. Our hosting platform offers:
+                        scalable infrastructure. Our <a href="../../odoo-hosting-2027.html">hosting platform</a> offers:
                     </p>
                     <ul>
                         <li>