feat: FAQ management from admin, public /faq, homepage section, llms.txt

- Backend: faq_questions table (schema + migration), CRUD + reorder API, Swagger docs
- Admin: FAQ page with create/edit, enable/disable, show on homepage, drag reorder
- Public /faq page fetches enabled FAQs from API; layout builds dynamic JSON-LD
- Homepage: FAQ section under Stay updated (homepage-enabled only) with See full FAQ link
- llms.txt: FAQ section uses homepage FAQs from API
- i18n: home.faq title/seeFull, admin FAQ nav

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/app/admin/layout.tsx

@@ -24,6 +24,7 @@ import {
   BanknotesIcon,
   QrCodeIcon,
   DocumentTextIcon,
+  QuestionMarkCircleIcon,
 } from '@heroicons/react/24/outline';
 import clsx from 'clsx';
 import { useState } from 'react';
@@ -69,6 +70,7 @@ export default function AdminLayout({
     { name: t('admin.nav.emails'), href: '/admin/emails', icon: InboxIcon },
     { name: t('admin.nav.gallery'), href: '/admin/gallery', icon: PhotoIcon },
     { name: locale === 'es' ? 'Páginas Legales' : 'Legal Pages', href: '/admin/legal-pages', icon: DocumentTextIcon },
+    { name: 'FAQ', href: '/admin/faq', icon: QuestionMarkCircleIcon },
     { name: locale === 'es' ? 'Configuración' : 'Settings', href: '/admin/settings', icon: Cog6ToothIcon },
   ];