fix(vikon): use correct token introspect endpoint for update system

Original vikon_core security.php validates tokens via:
  POST db-nica.ru/oauth2/resource/token/introspect
  Body: client_id=542&access_token=XXX

Our code was incorrectly using:
  GET auth.db-nica.ru/api/profile_applicant/check_access_token
  Header: Authorization: Bearer XXX

This was the WRONG endpoint — the profile check is for abitur forms,
not for the update system.

app/Containers/VikonIntegration/Tasks/ValidateTokenTask.php

@@ -8,16 +8,17 @@ class ValidateTokenTask
 {
     public function __construct(
         private readonly HttpTask $http,
+        private readonly string $clientId,
     ) {}
 
     public function run(string $accessToken): bool
     {
         try {
-            $response = $this->http->getWithToken(
-                'api/profile_applicant/check_access_token',
-                $accessToken,
-                'auth'
-            );
+            $response = $this->http->post('oauth2/resource/token/introspect', [
+                'client_id'    => $this->clientId,
+                'access_token' => $accessToken,
+            ]);
+
             return $response->successful();
         } catch (\Throwable $e) {
             Log::warning('Vikon token validation failed', ['error' => $e->getMessage()]);