Initial upload of BB-Apartment 2026 website.

Adds the complete Next.js website including i18n routing, house and
apartment pages, Beds24 v2 integration for live availability/pricing,
Stripe checkout, contact forms, Docker setup and deployment docs.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/error.tsx

@@ -0,0 +1,24 @@
+"use client";
+
+export default function GlobalError({
+  error,
+  reset,
+}: {
+  error: Error & { digest?: string };
+  reset: () => void;
+}) {
+  return (
+    <html>
+      <body className="min-h-screen flex flex-col items-center justify-center px-4 text-center bg-white text-brand-grey-dark">
+        <h2 className="text-2xl font-bold mb-4">Ein unerwarteter Fehler ist aufgetreten.</h2>
+        <p className="text-brand-grey mb-8">{error.message}</p>
+        <button
+          onClick={reset}
+          className="px-6 py-3 bg-brand-green text-white rounded-xl font-medium hover:bg-brand-green-dark transition-colors"
+        >
+          Erneut versuchen
+        </button>
+      </body>
+    </html>
+  );
+}