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

lib/supabase/server.ts

@@ -1,4 +1,5 @@
 import { createServerClient } from "@supabase/ssr";
+import { createClient as createSupabaseClient } from "@supabase/supabase-js";
 import { cookies } from "next/headers";
 import type { Database } from "@/types/database.types";
 
@@ -29,17 +30,10 @@ export const createClient = async () => {
 };
 
 // Client admin avec service role (webhooks, opérations admin)
+// Utilise @supabase/supabase-js directement (pas besoin de cookies)
 export const createAdminClient = () => {
-  return createServerClient<Database>(
+  return createSupabaseClient<Database>(
     process.env.NEXT_PUBLIC_SUPABASE_URL!,
-    process.env.SUPABASE_SERVICE_ROLE_KEY!,
-    {
-      cookies: {
-        getAll() {
-          return [];
-        },
-        setAll() {},
-      },
-    }
+    process.env.SUPABASE_SERVICE_ROLE_KEY!
   );
 };