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/how-to-install-odoo-modules-using-git.html

@@ -177,7 +177,7 @@
 
 <h2>7. What this means for the person who owns the business</h2>
 
-<p>You do not have to enjoy any of this. The point of running your system as a service is that the boring half - the repository, the keys, the restart, the version match - is somebody else's job. Add a capability when the business needs it, not when a project plan says so: a module goes in, the menu item appears, and your team uses it the same day.</p>
+<p>You do not have to enjoy any of this. The point of <a href="../../odoo-hosting-2027.html">running your system as a service</a> is that the boring half - the repository, the keys, the restart, the version match - is somebody else's job. Add a capability when the business needs it, not when a project plan says so: a module goes in, the menu item appears, and your team uses it the same day.</p>
 
 <p>If a console is not where you want to spend your afternoon, that is not a gap in your abilities. It is a job that should never have been yours in the first place.</p>
       </div>