feat: complete MVP foundation auth and dashboard

app/dashboard/analytics/page.tsx

@@ -0,0 +1,10 @@
+import { DashboardPlaceholderPage } from "@/components/dashboard-placeholder-page";
+
+export default function AnalyticsPage() {
+  return (
+    <DashboardPlaceholderPage
+      description="Kampagnenmetriken und Rybbit-Daten folgen in TASK-17 und TASK-19."
+      title="Analytics"
+    />
+  );
+}