Added "Services" page & refactor layout structure

- Introduced a new Services component with basic setup.
- Updated layout files to ensure consistent global styling references.
- Enhanced Navbar with pathname detection for active link styling.
- Fixed navigation link URL for "Leistungen" in constants.

app/contact/layout.tsx

@@ -1,5 +1,5 @@
 import type {Metadata} from "next";
-import "../(root)/globals.css";
+import "../globals.css";
 
 import Nav from "@/components/Navbar/Nav";
 import Footer from "@/components/Home/Footer/Footer";