Fix ticket page 500 from unbounded audit timeline (#112)

A ticket updated by hwmonDaemon had ~52k audit rows; getTicketTimeline()
loaded all of them and exhausted PHP's 128MB memory limit, so the ticket
page returned 500. Not related to the MCP server.

- getTicketTimeline() takes a limit (newest first). The ticket page shows
  the latest 500 events with a note when older ones are omitted; the JSON
  export caps at 5000.
- create_ticket_api.php: the description is refreshed on every run, and
  that alone wrote a reason-only audit row every few minutes per open
  ticket. Audit only real title/priority changes.
- create_ticket_api.php: after creating a brand-new ticket the dedup retry
  loop fell through into a second iteration on a closed connection,
  appending a 500 error body after the success response. Exit instead.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MGDKHiU5RJdo3dqQUDow3X

api/export_tickets.php

@@ -192,7 +192,7 @@ try {
 
         // Load flat comment list (no threading nesting in export)
         $rawComments = $commentModel->getCommentsByTicketId($ticket['ticket_id'], false);
-        $timeline    = $auditLogModel->getTicketTimeline((string)$ticket['ticket_id']);
+        $timeline    = $auditLogModel->getTicketTimeline((string)$ticket['ticket_id'], 5000);
 
         $comments = array_map(function ($c) {
             return [