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>

api/add_comment.php

@@ -99,6 +99,11 @@ try {
         exit;
     }
 
+    // Persist the trimmed text (not the raw client value) — matches update_comment.php
+    // and keeps stored comment_text free of leading whitespace that could shift a
+    // markdown-enabled comment's first line out of column 0 on reload.
+    $data['comment_text'] = $commentTextRaw;
+
     // Never trust a client-supplied display name — always attribute the comment to
     // the authenticated session user.
     $data['user_name'] = $currentUser['display_name'] ?? $currentUser['username'] ?? 'User';