Fix achievement badges visibility on desktop in game-stats.njk

[Copilot]

#achievement-badges started with hidden sm:flex as static classes. Since sm:flex has higher specificity than hidden, toggling hidden via JS was a no-op on sm+ screens — the container was always visible on desktop regardless of whether any badges were earned.

Changes

• HTML: Remove sm:flex from the static class list so the element starts fully hidden everywhere
• JS:
  • Add badgeContainer.innerHTML = "" to clear stale content on re-render
  • Track badgeCount as badges are appended
  • Replace missing visibility call with classList.toggle("sm:flex", badgeCount > 0) — dynamically applies responsive visibility only when badges exist

var badgeCount = 0;
Object.keys(icons).forEach(function (id) {
  if (earned[id]) {
    // ... append badge ...
    badgeCount += 1;
  }
});
badgeContainer.classList.toggle("sm:flex", badgeCount > 0);

Result: container is hidden everywhere when no badges are earned; hidden on mobile and visible as flex on sm+ when badges exist.