fix(icons): 清理 FA4 残留图标类，统一为 Font Awesome 5 约定

- 通用 fa fa-X 前缀改为 fa fas fa-X（12 个生产文件）
- 重命名图标映射：fa-sign-in→fa-sign-in-alt、fa-envelope-o→far fa-envelope、
  fa-trash-o→far fa-trash-alt、fa-file-image-o→far fa-file-image、
  fa-dot-circle-o→far fa-dot-circle、fa-play-circle-o→far fa-play-circle、
  fa-pencil→fas fa-pencil-alt
- 修复 FA5 中不存在的 fa-pencil-square→fas fa-edit

assets/js/cms-download.js

@@ -698,7 +698,7 @@
 				if (preview.balance_enough === false) {
 					if (preview.credits_url) {
 						body += '<a class="but c-red block mt6 aksrt-cashier__recharge" href="' + escapeAttr(preview.credits_url) + '">' +
-							'抱歉！余额不足，请先充值 <i class="ml6 fa fa-angle-right em12" aria-hidden="true"></i></a>';
+							'抱歉！余额不足，请先充值 <i class="ml6 fa fas fa-angle-right em12" aria-hidden="true"></i></a>';
 					} else {
 						body += '<div class="c-red mt6 aksrt-cashier__recharge">抱歉！余额不足，请先充值</div>';
 					}

assets/js/comment-ajax.js

@@ -133,7 +133,7 @@
         if (!result.success) { notyf((result.data && result.data.message) || result.message || '操作失败', 'danger'); return; }
         var pinned = !!(result.data && result.data.pinned);
         btn.setAttribute('data-pinned', pinned ? '1' : '0');
-        btn.innerHTML = '<i class="fa fa-thumbtack mr10 fa-fw" aria-hidden="true"></i>' + (pinned ? '取消置顶' : '设置置顶');
+        btn.innerHTML = '<i class="fa fas fa-thumbtack mr10 fa-fw" aria-hidden="true"></i>' + (pinned ? '取消置顶' : '设置置顶');
         syncPinnedBadge(commentEl, pinned);
         notyf(result.message || (pinned ? '评论已置顶。' : '已取消置顶。'), 'success');
       })
@@ -148,7 +148,7 @@
       badge = document.createElement('badge');
       badge.className = 'badge-topping jb-blue mr6 flex0';
       badge.title = '置顶评论';
-      badge.innerHTML = '<i class="fa fa-thumbtack" aria-hidden="true"></i>';
+      badge.innerHTML = '<i class="fa fas fa-thumbtack" aria-hidden="true"></i>';
       name.insertBefore(badge, name.firstChild);
     } else if (!pinned && badge) {
       badge.remove();