Replace spinners with skeleton loading states for faster perceived UX.

Add reusable Skeleton components and route-level loading files across public pages and admin lists so layouts stay stable while data loads.

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

frontend/src/app/admin/contacts/page.tsx

@@ -5,6 +5,7 @@ import { useLanguage } from '@/context/LanguageContext';
 import { contactsApi, Contact } from '@/lib/api';
 import Card from '@/components/ui/Card';
 import Button from '@/components/ui/Button';
+import { Skeleton, SkeletonText, CardListSkeleton } from '@/components/ui/Skeleton';
 import { EnvelopeIcon, EnvelopeOpenIcon, CheckIcon } from '@heroicons/react/24/outline';
 import toast from 'react-hot-toast';
 import { parseDate } from '@/lib/utils';
@@ -65,8 +66,21 @@ export default function AdminContactsPage() {
 
   if (loading) {
     return (
-      <div className="flex items-center justify-center py-12">
-        <div className="animate-spin w-8 h-8 border-4 border-primary-yellow border-t-transparent rounded-full" />
+      <div>
+        <div className="flex items-center justify-between mb-6">
+          <Skeleton className="h-8 w-48" />
+        </div>
+        <div className="grid grid-cols-1 lg:grid-cols-3 gap-6">
+          <div className="lg:col-span-1">
+            <CardListSkeleton count={5} />
+          </div>
+          <div className="lg:col-span-2">
+            <div className="bg-white rounded-card shadow-card p-6">
+              <Skeleton className="h-6 w-1/3" />
+              <SkeletonText lines={4} className="mt-6" />
+            </div>
+          </div>
+        </div>
       </div>
     );
   }