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/linktree/page.tsx

@@ -73,8 +73,22 @@ export default function LinktreePage() {
           </h2>
           
           {loading ? (
-            <div className="bg-white/10 backdrop-blur-sm rounded-2xl p-6 text-center">
-              <div className="animate-spin w-6 h-6 border-2 border-primary-yellow border-t-transparent rounded-full mx-auto" />
+            <div
+              className="bg-white/10 backdrop-blur-sm rounded-2xl p-5 border border-white/10 animate-pulse"
+              role="status"
+              aria-busy="true"
+            >
+              <span className="sr-only">Loading…</span>
+              <div className="h-6 w-2/3 rounded-lg bg-white/15" />
+              <div className="mt-3 space-y-2">
+                <div className="h-4 w-3/4 rounded-lg bg-white/15" />
+                <div className="h-4 w-1/2 rounded-lg bg-white/15" />
+              </div>
+              <div className="mt-4 flex items-center justify-between">
+                <div className="h-5 w-20 rounded-lg bg-white/15" />
+                <div className="h-4 w-24 rounded-lg bg-white/15" />
+              </div>
+              <div className="mt-4 h-12 rounded-xl bg-white/15" />
             </div>
           ) : nextEvent ? (
             <Link href={`/events/${nextEvent.slug}`} className="block group">