fix: Use parseMarkdown instead of marked.parse for comment preview

Fixed markdown preview for comments by replacing marked.parse() calls
with parseMarkdown() function. The application uses a custom markdown
parser (markdown.js), not the marked.js library.

Changes:
- togglePreview(): Use parseMarkdown() instead of marked.parse()
- updatePreview(): Use parseMarkdown() instead of marked.parse()

Resolves issue where markdown preview didn't work for comments but
worked after posting.

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

assets/js/ticket.js

@@ -224,7 +224,7 @@ function togglePreview() {
     preview.style.display = isPreviewEnabled ? 'block' : 'none';
     
     if (isPreviewEnabled) {
-        preview.innerHTML = marked.parse(textarea.value);
+        preview.innerHTML = parseMarkdown(textarea.value);
         textarea.addEventListener('input', updatePreview);
     } else {
         textarea.removeEventListener('input', updatePreview);
@@ -237,8 +237,8 @@ function updatePreview() {
     const isMarkdownEnabled = document.getElementById('markdownMaster').checked;
     
     if (isMarkdownEnabled && commentText.trim()) {
-        // For markdown preview, use marked.parse which handles line breaks correctly
-        previewDiv.innerHTML = marked.parse(commentText);
+        // For markdown preview, use parseMarkdown which handles line breaks correctly
+        previewDiv.innerHTML = parseMarkdown(commentText);
         previewDiv.style.display = 'block';
     } else {
         previewDiv.style.display = 'none';