feat(staging): inbound links so /odoo-staging-environment/ is not an orphan

The copy's 'Into this page' table, applied as single additive sentences:
- support.html: the 'error 500 after a git check in' FAQ answer links
  'test it safely first'.
- blog/posts/speed-run-backup.html: end of the post links
  'what a staging environment is, and why you probably do not need one'.
- odoo-hosting-2027.html: one contextual note by the backup/module rows
  links 'do you need a staging environment?'.
- index.html: one FAQ card 'Do you need an Odoo staging environment?'.
No footer change. No new impeccable finding category.

support.html

@@ -439,6 +439,7 @@
                         </button>
                         <div class="faq-answer">
                             <p>If you've pushed a new module to the server and it prevents the service from starting, first revert your changes in Git and push the corrected version back to the server. Then open the support chat — you'll need your UUID (sent in the confirmation email). After you tell our chatbot to git pull and restart the server, you'll receive a confirmation email; once confirmed, we'll bring your Odoo instance back online.</p>
+                            <p>Before you check in a change like this, read <a href="/odoo-staging-environment/">test it safely first</a>: a staging environment is what stops a bad check-in taking your server down, and most small businesses do not need one.</p>
                         </div>
                     </div>
                     <div class="faq-item">