chore: Remove library link from navbar

Library is now accessed per-campaign via the campaign detail page.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/src/shared/components/layout.tsx

@@ -42,12 +42,6 @@ export function Layout() {
               >
                 Kampagnen
               </Link>
-              <Link
-                to="/library"
-                className="text-sm text-text-secondary hover:text-text-primary transition-colors"
-              >
-                Bibliothek
-              </Link>
             </nav>
 
             {/* User Menu */}