Fix leading-zero ticket ID handling across API and UI

- dashboard.js: use String(cb.value) instead of parseInt() in
  getSelectedTicketIds() so zero-padded IDs like 000123456 are
  preserved when sent to bulk_operation.php
- DashboardView.php: remove (int) cast on data-ticket-id attribute
  for quick-status button; was stripping leading zeros
- TicketView.php: remove (int) cast on export URL ticket_id param
- update_ticket.php: preserve ticket_id as string via trim((string)...)
- add_comment.php: preserve ticket_id as string; validate with
  ctype_digit instead of (int) cast so comments are stored with the
  canonical zero-padded ID matching the tickets table
- export_tickets.php: validate singleId as string to avoid stripping
  leading zeros in the export endpoint
- notifications.php: preserve ticket_id strings in URLs and ticket
  ownership checks; index myTicketIds by both int and string forms
  for robust lookup regardless of how audit_log stored the ID
- TicketController.php: fix inline dependency insert — column was
  wrong (depends_on_ticket_id → depends_on_id) and bind types were
  wrong ("iii" → "ssi"); feature was silently broken

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

api/export_tickets.php

@@ -43,7 +43,8 @@ try {
     $search = isset($_GET['search']) ? trim($_GET['search']) : null;
     $format   = isset($_GET['format'])    ? $_GET['format']    : 'csv';
     $ticketIds = isset($_GET['ticket_ids']) ? $_GET['ticket_ids'] : null;
-    $singleId  = isset($_GET['ticket_id']) ? (int)$_GET['ticket_id'] : null;
+    $singleIdRaw = isset($_GET['ticket_id']) ? trim($_GET['ticket_id']) : null;
+    $singleId    = ($singleIdRaw !== null && ctype_digit($singleIdRaw) && (int)$singleIdRaw > 0) ? $singleIdRaw : null;
 
     // Initialize model
     $ticketModel = new TicketModel($conn);