feat: integrate landing page with real API and add CMS to backoffice

Landing page:
- Events page now fetches from /v1/landing/cms/events (was hardcoded JSON)
- Testimonials section and page fetch from /v1/landing/cms/testimonials
- Removed dummy data, uses ISR with 60s revalidation
- Replaced thumbnail images with text-based cards (API has no thumbnails)
- Avatar initials for testimonials instead of placeholder images

Backoffice CMS:
- Added Events management page (/cms-events) with full CRUD
- Added Testimonials management page (/cms-testimonials) with full CRUD
- Both follow existing backoffice patterns (DataTable, modals, search, pagination)
- Added CMS section to sidebar navigation

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

libs/ui/src/organisms/backoffice-sidebar/backoffice-sidebar.tsx

@@ -2,10 +2,12 @@ import {
   AppstoreOutlined,
   AuditOutlined,
   BookOutlined,
+  CalendarOutlined,
   CommentOutlined,
   DownOutlined,
   InboxOutlined,
   LogoutOutlined,
+  MessageOutlined,
   ReadOutlined,
   ReloadOutlined,
   RightOutlined,
@@ -118,6 +120,22 @@ const MENUS: MenuItem[] = [
       },
     ],
   },
+  {
+    label: 'CMS',
+    icon: <BookOutlined className="text-[20px]" />,
+    children: [
+      {
+        label: 'Events',
+        href: '/cms-events',
+        icon: <CalendarOutlined className="text-[20px]" />,
+      },
+      {
+        label: 'Testimonials',
+        href: '/cms-testimonials',
+        icon: <MessageOutlined className="text-[20px]" />,
+      },
+    ],
+  },
   {
     label: 'Permissions',
     href: '/permissions',