fix(ifc-converter): broken Contributions GitHub URL (#335)

apps/ifc-converter/app/page.tsx pointed at
github.com/pascalorg/editor/apps/ifc-converter which 404s. The
canonical path includes /tree/main/. Same URL is reused by the
forthcoming community /ifc page (in pascalorg/private-editor) so
keeping them consistent matters.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/ifc-converter/app/page.tsx

@@ -16,7 +16,7 @@ export default function HomePage() {
           elements, default-height walls, skipped items.{' '}
           <a
             className="font-medium underline decoration-amber-400 underline-offset-2 hover:text-amber-700"
-            href="https://github.com/pascalorg/editor/apps/ifc-converter"
+            href="https://github.com/pascalorg/editor/tree/main/apps/ifc-converter"
             rel="noopener noreferrer"
             target="_blank"
           >