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/oca-paraguay-internationalization-hackathon.html

@@ -87,7 +87,7 @@
 
 <h2>Why we support it</h2>
 
-<p>Localisation is the part of open source no vendor ships for you: the chart of accounts, the taxes, electronic invoicing, the labels in your own language. It exists because a community maintains it. We run Odoo Community hosting, so a stronger Paraguayan localisation is our customers' business — and ours.</p>
+<p>Localisation is the part of open source no vendor ships for you: the chart of accounts, the taxes, electronic invoicing, the labels in your own language. It exists because a community maintains it. <a href="../../odoo-hosting-2027.html">We run Odoo Community hosting</a>, so a stronger Paraguayan localisation is our customers' business — and ours.</p>
 
 <p>Sign up at <strong>oca-py.org</strong>: your name, your GitHub user and how you can contribute. Open to all levels.</p>
       </div>