fix: Resolve multiple UI and API bugs

- Remove is_active filter from get_users.php (column doesn't exist)
- Fix ticket ID validation regex in upload_attachment.php (9-digit format)
- Fix createSettingsModal reference to use openSettingsModal from settings.js
- Add error handling for dependencies tab to prevent infinite loading
- Add try-catch wrapper to ticket_dependencies.php API
- Make export dropdown visible only when tickets are selected
- Export only selected tickets instead of all filtered tickets

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

api/export_tickets.php

@@ -47,13 +47,31 @@ try {
     $type = isset($_GET['type']) ? $_GET['type'] : null;
     $search = isset($_GET['search']) ? trim($_GET['search']) : null;
     $format = isset($_GET['format']) ? $_GET['format'] : 'csv';
+    $ticketIds = isset($_GET['ticket_ids']) ? $_GET['ticket_ids'] : null;
 
     // Initialize model
     $ticketModel = new TicketModel($conn);
 
-    // Get all tickets (no pagination for export)
-    $result = $ticketModel->getAllTickets(1, 10000, $status, 'created_at', 'desc', $category, $type, $search);
-    $tickets = $result['tickets'];
+    // Check if specific ticket IDs are provided
+    if ($ticketIds) {
+        // Parse and validate ticket IDs
+        $ticketIdArray = array_filter(array_map('trim', explode(',', $ticketIds)));
+        if (empty($ticketIdArray)) {
+            header('Content-Type: application/json');
+            http_response_code(400);
+            echo json_encode(['success' => false, 'error' => 'No valid ticket IDs provided']);
+            exit;
+        }
+
+        // Get specific tickets by IDs
+        $tickets = $ticketModel->getTicketsByIds($ticketIdArray);
+        // Convert associative array to indexed array
+        $tickets = array_values($tickets);
+    } else {
+        // Get all tickets with filters (no pagination for export)
+        $result = $ticketModel->getAllTickets(1, 10000, $status, 'created_at', 'desc', $category, $type, $search);
+        $tickets = $result['tickets'];
+    }
 
     if ($format === 'csv') {
         // CSV Export