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>

views/DashboardView.php

@@ -762,7 +762,7 @@ include __DIR__ . '/layout_header.php';
                               aria-label="View ticket <?= htmlspecialchars($row['ticket_id']) ?>">View</button>
                       <button type="button" class="lt-btn lt-btn-sm lt-btn-ghost"
                               data-action="quick-status"
-                              data-ticket-id="<?= (int)$row['ticket_id'] ?>"
+                              data-ticket-id="<?= htmlspecialchars($row['ticket_id']) ?>"
                               data-status="<?= htmlspecialchars($row['status'], ENT_QUOTES) ?>"
                               aria-label="Change status">&#x7E;</button>
                       <button type="button" class="lt-btn lt-btn-sm lt-btn-ghost"