fix: use connection() API to force dynamic rendering in Next.js 15 (qa-requested)

- Add connection() API call to guarantee dynamic rendering
- Fixes critical auth bypass where page was still being pre-rendered
- Previous fix (force-dynamic) was insufficient in Next.js 15
- connection() API is the official Next.js 15 recommendation

Resolves QA Session 2 Critical Issue #1

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

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

@@ -1,3 +1,4 @@
+import { connection } from 'next/server';
 import { setRequestLocale } from 'next-intl/server';
 import type { Metadata } from 'next';
 import { redirect } from 'next/navigation';
@@ -34,6 +35,9 @@ export async function generateMetadata({ params }: Props): Promise<Metadata> {
 }
 
 export default async function DashboardPage({ params }: Props) {
+  // CRITICAL: Use connection() API to guarantee dynamic rendering in Next.js 15
+  await connection();
+
   const { locale } = await params;
   setRequestLocale(locale);