fix: forward session token in admin SSR load functions

Admin list queries (users, videos, articles) were using getGraphQLClient
without auth credentials, causing silent 403s on server-side loads. Now
extract session_token cookie and pass it to getAuthClient so the backend
sees the admin session on SSR requests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/frontend/src/routes/admin/articles/+page.server.ts

@@ -1,6 +1,7 @@
 import { adminListArticles } from "$lib/services";
 
-export async function load({ fetch }) {
-  const articles = await adminListArticles(fetch).catch(() => []);
+export async function load({ fetch, cookies }) {
+  const token = cookies.get("session_token") || "";
+  const articles = await adminListArticles(fetch, token).catch(() => []);
   return { articles };
 }