Fix comment avatar, activity log labels, and ticket update permissions

- add_comment.php: include user_id in response for avatar rendering
- ticket.js: add buildCommentElement() helper that matches server-rendered
  comment structure (avatar, edit/delete buttons, textarea); use it in
  addComment() and submitReply() so new comments show the avatar immediately
- AuditLogModel: logCommentCreate uses action_type='comment' not 'create'
- TicketView: formatAction handles entity_type='comment' with action_type='create'
  for existing DB records; prevents "created this ticket" showing for comments
- update_ticket.php: remove owner/assignee restriction so any authenticated
  team member can update ticket status and fields

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

models/AuditLogModel.php

@@ -369,7 +369,7 @@ class AuditLogModel {
     public function logCommentCreate($userId, $commentId, $ticketId) {
         return $this->log(
             $userId,
-            'create',
+            'comment',
             'comment',
             (string)$commentId,
             ['ticket_id' => $ticketId]