feat: complete MVP foundation auth and dashboard

app/dashboard/settings/page.tsx

@@ -0,0 +1,10 @@
+import { DashboardPlaceholderPage } from "@/components/dashboard-placeholder-page";
+
+export default function SettingsPage() {
+  return (
+    <DashboardPlaceholderPage
+      description="Provider-Status, Secrets-Hinweise und Workspace-Einstellungen folgen mit den Integrationen."
+      title="Settings"
+    />
+  );
+}