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/my-first-post.html

@@ -234,8 +234,8 @@
                     </p>
                     <h2>Step 1: Choose Your Plan</h2>
                     <p>
-                        At ODOO4projects we offer four plans designed to grow
-                        with you. If you're just getting started,
+                        At ODOO4projects we offer <a href="../../index.html#pricing">four plans designed to grow
+                        with you</a>. If you're just getting started,
                         <strong>Side Hustle</strong> gives you a fully
                         functional Odoo CE instance with 1 backup slot and
                         domain mapping. As your needs grow, you can upgrade to
@@ -275,7 +275,7 @@ Admin credentials: sent via email</code></pre>
                     <p>
                         With your instance live and your domain mapped, you're
                         ready to install apps, configure users, and customize
-                        your workflows. Need help? Our support team is just a
+                        your workflows. Need help? Our <a href="../../support.html">support team</a> is just a
                         message away.
                     </p>
                     <div class="cta-box">