auto-claude: subtask-2-1 - Add server-side auth check to dashboard page

- Added server-side authentication check in DashboardPage component
- Created Supabase client using createClient from @/lib/supabase/server
- Check user authentication with getUser() before rendering
- Redirect to /${locale}/login if user is not authenticated
- Provides defense-in-depth security alongside middleware protection

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/app/[locale]/dashboard/page.tsx

@@ -1,6 +1,8 @@
 import { setRequestLocale } from 'next-intl/server';
 import type { Metadata } from 'next';
+import { redirect } from 'next/navigation';
 import DashboardContent from '@/components/auth/DashboardContent';
+import { createClient } from '@/lib/supabase/server';
 
 type Props = {
   params: Promise<{ locale: string }>;
@@ -32,5 +34,13 @@ export default async function DashboardPage({ params }: Props) {
   const { locale } = await params;
   setRequestLocale(locale);
 
+  // Server-side auth check (defense-in-depth)
+  const supabase = await createClient();
+  const { data: { user } } = await supabase.auth.getUser();
+
+  if (!user) {
+    redirect(`/${locale}/login`);
+  }
+
   return <DashboardContent />;
 }