feat(provider): implement ping and probe on GitHub, GitLab, and Gitea

Add getName() and ping() to each provider and wire ProbeTrait. Make
all classes final, add strict_types declarations, and replace generic
RuntimeException with typed HTTP exceptions so probe() can classify
auth failures and unreachable endpoints correctly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/Service/GitLabProvider.php

@@ -1,8 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 namespace App\Service;
 
 use Psr\Log\LoggerInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 
 /**
@@ -11,8 +14,10 @@ use Symfony\Contracts\HttpClient\HttpClientInterface;
  * Required token scopes: read_user, read_api
  * Works with both gitlab.com and self-hosted instances.
  */
-class GitLabProvider implements ProviderInterface
+final class GitLabProvider implements ProviderInterface
 {
+    use ProbeTrait;
+
     public function __construct(
         private readonly HttpClientInterface $client,
         private readonly string $username,
@@ -21,11 +26,25 @@ class GitLabProvider implements ProviderInterface
         private readonly string $baseUrl = '',
     ) {}
 
+    public function getName(): string
+    {
+        return 'gitlab';
+    }
+
     public function isConfigured(): bool
     {
         return $this->username !== '' && $this->token !== '';
     }
 
+    public function ping(): void
+    {
+        $baseUrl = rtrim($this->baseUrl !== '' ? $this->baseUrl : 'https://gitlab.com', '/');
+
+        $this->client->request('GET', "$baseUrl/api/v4/user", [
+            'headers' => ['PRIVATE-TOKEN' => $this->token],
+        ])->getContent();
+    }
+
     /**
      * @return array<string, int>  date (Y-m-d) => event count
      */
@@ -35,7 +54,6 @@ class GitLabProvider implements ProviderInterface
 
         $this->logger->debug('GitLabProvider: fetching contributions', ['user' => $this->username, 'url' => $baseUrl]);
 
-        // Resolve numeric user ID from username
         $userResponse = $this->client->request('GET', "$baseUrl/api/v4/users", [
             'headers' => ['PRIVATE-TOKEN' => $this->token],
             'query'   => ['username' => $this->username],
@@ -43,7 +61,7 @@ class GitLabProvider implements ProviderInterface
 
         $users = $userResponse->toArray();
         if (empty($users)) {
-            throw new \RuntimeException("GitLab: user '{$this->username}' not found on $baseUrl");
+            throw new NotFoundHttpException("GitLab: user '{$this->username}' not found on $baseUrl");
         }
         $userId = $users[0]['id'];