Add usernames and sudo_usernames fields to VM request form

- DB: add usernames/sudo_usernames columns to vm_requests table
- create.php: add form inputs for usernames and sudo_usernames
- send.php: capture, validate, and store both fields in DB
- netbox_integration/netbox_api.php: pass custom_fields to NetBox VM API
- requests.php: show usernames/sudo_usernames in request list

netbox_integration/netbox_api.php

@@ -119,6 +119,18 @@ class NetBoxClient {
             'description' => $params['description'] ?? '',
         ];
 
+        // Custom fields: usernames and sudo_usernames
+        $cf = [];
+        if (!empty($params['usernames'])) {
+            $cf['usernames'] = $params['usernames'];
+        }
+        if (!empty($params['sudo_usernames'])) {
+            $cf['sudo_usernames'] = $params['sudo_usernames'];
+        }
+        if (!empty($cf)) {
+            $payload['custom_fields'] = $cf;
+        }
+
         // Tag lookup for domain — tags must be numeric IDs in the NetBox API
         if (!empty($params['domain'])) {
             $tag = $this->findTag($params['domain']);