Fix markdown CSS not applying to comments — add lt-markdown class

comment-text divs with data-markdown were never getting the lt-markdown
class, so all scoped CSS (ul/ol/li bullets, mark, del, task items, etc.)
had no effect. Fixed in PHP template, JS comment builder, and
renderMarkdownComments().

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/js/ticket.js

@@ -244,7 +244,7 @@ function buildCommentElement(opts) {
             '<span class="comment-date lt-text-xs lt-text-muted">' + lt.escHtml(opts.createdAt) + '</span>' +
             '<div class="comment-actions lt-btn-group">' + replyBtn + modBtns + '</div>' +
           '</div>' +
-          '<div class="comment-text" id="comment-text-' + opts.commentId + '"' +
+          '<div class="comment-text' + (opts.isMarkdown ? ' lt-markdown' : '') + '" id="comment-text-' + opts.commentId + '"' +
             (opts.isMarkdown ? ' data-markdown data-rendered="1"' : '') + '>' +
             opts.commentText +
           '</div>' +