feat(Navbar): wire anchor links to page sections

Werkzeuge→#werkzeuge, Blog→#blog, Über Björn→#ueber-bjoern.
Shop remains /shop (no matching section). Added matching id attributes
to Tools, Blog and About section root elements.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/components/About.tsx

@@ -1,6 +1,6 @@
 export function About() {
   return (
-    <section className="bg-[#111] flex items-stretch w-full">
+    <section id="ueber-bjoern" className="bg-[#111] flex items-stretch w-full">
 
       {/* Left: text content */}
       <div className="flex-1 flex flex-col gap-4 justify-center px-[5rem] py-8 min-w-0">