feat(seo): add /what-can-i-use-odoo-for/ guide page, linked from the homepage and support FAQ

Modelled on odoo-community-upgrade.html (top bar, band rhythm, FAQ details).
Copy published verbatim from the copywriter's 2026-10-28 file: 58-char title,
157-char meta, the six outbound internal links and the WebPage+Article+FAQPage+
BreadcrumbList @graph. Nine FAQ questions marked plausible-event-name=FAQ (no
event fires on page load). Sitemap + llms.txt list the new URL. Inbound links:
one from the homepage FAQ card, one from the support FAQ answer. Nothing else
moves; no footer change.

index.html

@@ -380,7 +380,7 @@
           </div>
           <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>ODOO Community? What can it do?</span> <i class="fas fa-chevron-down"></i></div>
-            <div class="faq-a"><p>Inventory, accounting, CRM, sales, manufacturing, HR — all in one system. Free and fully open-source.</p></div>
+            <div class="faq-a"><p>Inventory, accounting, CRM, sales, manufacturing, HR — all in one system. Free and fully open-source. <a href="what-can-i-use-odoo-for/">What you can use Odoo for, in plain English</a>.</p></div>
           </div>
           <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>Do you have an affiliate program?</span> <i class="fas fa-chevron-down"></i></div>