Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/app/admin/catalog/[id]/loading.tsx

@@ -0,0 +1,41 @@
+import { Skeleton } from '@/components/ui/skeleton'
+
+export default function CatalogDetailLoading() {
+  return (
+    <div className="space-y-6">
+      {/* Breadcrumb */}
+      <div className="flex items-center gap-2">
+        <Skeleton className="h-4 w-16" />
+        <Skeleton className="h-4 w-4" />
+        <Skeleton className="h-4 w-24" />
+        <Skeleton className="h-4 w-4" />
+        <Skeleton className="h-4 w-20" />
+      </div>
+
+      {/* Title */}
+      <div>
+        <Skeleton className="h-9 w-64" />
+        <Skeleton className="h-5 w-40 mt-2" />
+      </div>
+
+      {/* Tabs */}
+      <div className="space-y-4">
+        <div className="flex gap-2 border-b pb-2">
+          {Array.from({ length: 4 }).map((_, i) => (
+            <Skeleton key={i} className="h-9 w-24 rounded-md" />
+          ))}
+        </div>
+
+        {/* Tab content */}
+        <div className="rounded-lg border bg-card p-6 space-y-4">
+          {Array.from({ length: 6 }).map((_, i) => (
+            <div key={i} className="space-y-2">
+              <Skeleton className="h-4 w-24" />
+              <Skeleton className="h-10 w-full" />
+            </div>
+          ))}
+        </div>
+      </div>
+    </div>
+  )
+}