seo: improve metadata base and sitemap resilience

Co-authored-by: dennis <dennis@konkol.net>

app/layout.tsx

@@ -4,6 +4,7 @@ import { Inter } from "next/font/google";
 import React from "react";
 import ClientProviders from "./components/ClientProviders";
 import { cookies } from "next/headers";
+import { getBaseUrl } from "@/lib/seo";
 
 const inter = Inter({
   variable: "--font-inter",
@@ -30,6 +31,7 @@ export default async function RootLayout({
 }
 
 export const metadata: Metadata = {
+  metadataBase: new URL(getBaseUrl()),
   title: "Dennis Konkol | Portfolio",
   description:
     "Portfolio of Dennis Konkol, a student and software engineer based in Osnabrück, Germany. Passionate about technology, coding, and solving real-world problems.",