Trim comment text before persisting, not just for validation

add_comment.php computed a trimmed copy of comment_text only to check
for empty input, then passed the original untrimmed $data through to
CommentModel::addComment(), so any leading/trailing whitespace the
user typed (or pasted) was written to ticket_comments.comment_text as-is.
update_comment.php already trims before saving edits, so a comment
could pass through this endpoint once with untrimmed text (creation)
and be silently corrected the moment it was next edited — inconsistent
storage that, combined with the markdown parser's line-anchored regexes
(headings, tables, lists all match on ^), could make a markdown-enabled
comment mis-render after a reload depending on whether its first line
carried leading whitespace.

Also trims in the "Load more comments" pagination re-render path in
TicketView.php, matching the two on-load renderers in markdown.js so
all three code paths that call parseMarkdown() on stored comment text
treat leading whitespace consistently.

Closes #18

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

views/TicketView.php

@@ -1219,7 +1219,7 @@ document.addEventListener('DOMContentLoaded', function () {
                 if (typeof parseMarkdown === 'function') {
                     list.querySelectorAll('.comment-text[data-markdown]').forEach(function (el) {
                         if (!el.dataset.rendered) {
-                            el.innerHTML = parseMarkdown(el.textContent);
+                            el.innerHTML = parseMarkdown(el.textContent.trim());
                             el.dataset.rendered = '1';
                         }
                     });