fix: resolve __dirname error by forcing Node.js runtime on all server routes

- Add serverExternalPackages for @supabase/ssr in next.config.ts
- Add export const runtime = 'nodejs' to all pages/routes using Supabase
- Replace createAdminClient to use @supabase/supabase-js directly (no SSR)
- Prevents @supabase/ssr from running in Edge runtime on Vercel

https://claude.ai/code/session_01H2aRGDaKgarPvhay2HxN6Y

app/(protected)/layout.tsx

@@ -3,6 +3,8 @@ import { createClient } from "@/lib/supabase/server";
 import Sidebar from "@/components/dashboard/Sidebar";
 import type { Profile } from "@/types/database.types";
 
+export const runtime = "nodejs";
+
 export default async function DashboardLayout({
   children,
 }: {