[Feat] Pulse Admin Dashboard - manually grant plans to organizations

- Add admin layout with /api/admin/me check and access denial
- Add admin pages: dashboard, orgs list, org detail with grant form
- Add lib/api/admin.ts client for admin endpoints

Made-with: Cursor

app/admin/page.tsx

@@ -0,0 +1,24 @@
+'use client'
+
+import Link from 'next/link'
+import { Card, CardHeader, CardTitle, CardDescription, CardContent } from '@ciphera-net/ui'
+
+export default function AdminDashboard() {
+  return (
+    <div className="grid gap-6 md:grid-cols-2 lg:grid-cols-3">
+      <Link href="/admin/orgs" className="block transition-transform hover:scale-[1.02]">
+        <Card>
+          <CardHeader>
+            <CardTitle>Organizations</CardTitle>
+            <CardDescription>Manage organization plans and limits</CardDescription>
+          </CardHeader>
+          <CardContent>
+            <p className="text-sm text-neutral-500 dark:text-neutral-400">
+              View all organizations, check billing status, and manually grant plans.
+            </p>
+          </CardContent>
+        </Card>
+      </Link>
+    </div>
+  )
+}