refactor: update font imports and variables

- Replaced GeistSans and GeistMono with Inter and JetBrainsMono in globals.css and layout.tsx.
- Updated font variable names to reflect the new font choices in fonts.ts.

components/layout/footer.tsx

@@ -9,15 +9,14 @@ const Footer = () => {
       <Link href="/license" className="underline underline-offset-4">
         {siteConfig.license}
       </Link>
-      . Code is{" "}
+      . View source on{" "}
       <a
         href={`https://github.com/${env.NEXT_PUBLIC_GITHUB_REPO}`}
         target="_blank"
         rel="noopener noreferrer"
-        title="View Source on GitHub"
         className="underline underline-offset-4"
       >
-        open source
+        GitHub
       </a>
       .
     </footer>