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>

controllers/TicketController.php

@@ -126,12 +126,12 @@ class TicketController {
                 }
 
                 // Auto-link as duplicate if requested from create form
-                $linkDupOf = isset($_POST['link_duplicate_of']) ? (int)$_POST['link_duplicate_of'] : 0;
-                if ($linkDupOf > 0) {
-                    $depSql = "INSERT IGNORE INTO ticket_dependencies (ticket_id, depends_on_ticket_id, dependency_type, created_by)
+                $linkDupOfRaw = trim($_POST['link_duplicate_of'] ?? '');
+                if ($linkDupOfRaw !== '' && ctype_digit($linkDupOfRaw)) {
+                    $depSql = "INSERT IGNORE INTO ticket_dependencies (ticket_id, depends_on_id, dependency_type, created_by)
                                VALUES (?, ?, 'duplicates', ?)";
                     $depStmt = $this->conn->prepare($depSql);
-                    $depStmt->bind_param("iii", $result['ticket_id'], $linkDupOf, $userId);
+                    $depStmt->bind_param("ssi", $result['ticket_id'], $linkDupOfRaw, $userId);
                     $depStmt->execute();
                     $depStmt->close();
                 }