Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/app/admin/users/loading.tsx

@@ -0,0 +1,46 @@
+import { Skeleton } from '@/components/ui/skeleton'
+
+export default function UsersLoading() {
+  return (
+    <div className="space-y-6">
+      <div className="flex items-center justify-between">
+        <div>
+          <Skeleton className="h-9 w-32" />
+          <Skeleton className="h-5 w-56 mt-2" />
+        </div>
+        <Skeleton className="h-10 w-28" />
+      </div>
+
+      {/* Toolbar */}
+      <div className="flex items-center gap-3">
+        <Skeleton className="h-10 w-64" />
+        <Skeleton className="h-10 w-24" />
+        <Skeleton className="h-10 w-[100px]" />
+      </div>
+
+      {/* Table */}
+      <div className="rounded-md border">
+        <div className="border-b px-4 py-3">
+          <div className="flex gap-8">
+            {Array.from({ length: 6 }).map((_, i) => (
+              <Skeleton key={i} className="h-4 w-20" />
+            ))}
+          </div>
+        </div>
+        {Array.from({ length: 10 }).map((_, i) => (
+          <div key={i} className="flex items-center gap-8 px-4 py-3 border-b last:border-0">
+            <Skeleton className="h-4 w-10" />
+            <div className="flex items-center gap-2">
+              <Skeleton className="h-8 w-8 rounded" />
+              <Skeleton className="h-4 w-24" />
+            </div>
+            <Skeleton className="h-4 w-36" />
+            <Skeleton className="h-5 w-14 rounded-full" />
+            <Skeleton className="h-4 w-16" />
+            <Skeleton className="h-5 w-14 rounded-full" />
+          </div>
+        ))}
+      </div>
+    </div>
+  )
+}