Replace timezone with full ISO datetime in partner_metadata

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

Author: vinogradovkonst

src/layouts/Layout.astro

@@ -335,7 +335,7 @@ import { OpenPanelComponent } from '@openpanel/astro';
         visitor_id: window.__oseVisitorId,
         source_page: window.location.pathname,
         entry_page: sessionStorage.getItem('ose_entry') || window.location.pathname,
-        timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
+        datetime: new Date().toISOString(),
         locale: navigator.language,
         utm_source: urlParams.get('utm_source') || undefined,
         utm_medium: urlParams.get('utm_medium') || undefined,