Add YouTube channel link to the home page header

Subtle link in the top-right of the home page header pointing at
https://www.youtube.com/@AIWentNonsense. Lucide Youtube icon plus
'YouTube' label, hidden on small screens. Opens in a new tab with
rel=noopener noreferrer. Sits to the left of the (conditional)
'Server offline' indicator.

src/pages/HomePage.tsx

@@ -1,4 +1,5 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
+import { Youtube } from "lucide-react";
 import { InputPanel } from "../components/InputPanel";
 import type { InputValues } from "../components/InputPanel";
 import {
@@ -311,6 +312,16 @@ export function HomePage() {
             </span>
           </div>
           <div className="flex items-center gap-3">
+            <a
+              href="https://www.youtube.com/@AIWentNonsense"
+              target="_blank"
+              rel="noopener noreferrer"
+              className="inline-flex items-center gap-1.5 text-xs text-fg-muted hover:text-fg transition-colors"
+              title="AI Went Nonsense on YouTube"
+            >
+              <Youtube className="w-4 h-4" />
+              <span className="hidden sm:inline">YouTube</span>
+            </a>
             {serverOk === false && (
               <span
                 className="text-xs text-rose-300 hidden sm:inline"