homepage: AI section to the bottom; model-only AI descriptions

The user page now orders Web Apps, Media Library Apps, AI — the models sit
at the bottom, below the apps people click. The AI card and /docs#models
descriptions drop the infrastructure (runtimes, GPUs, tensor parallelism,
draft heads) in favor of what users care about: the hosted model, its
size, the context/parallel capacity, and what it's good at.

shared/homepage/app.js

@@ -10,7 +10,7 @@ const CATEGORY = window.location.pathname.indexOf('/admin') !== -1 ? 'admin' : '
 // same renderSection()/renderPanel() below. SECTION_ORDER fixes each page's
 // section order; a section with no services renders nothing.
 const SECTION_ORDER = {
-    user: ['AI', 'Web Apps', 'Media Library Apps'],
+    user: ['Web Apps', 'Media Library Apps', 'AI'],
     admin: ['Media Library Apps', 'Observability', 'AI', 'Infrastructure'],
 };