feat: Update authentication header and user agent in Client.php

Replaced 'Authorization' header with 'X-FIRE-APIKEY' for API authentication. Updated 'User-Agent' to 'FireClient/1.0' to align with new client identification standards.

Author: efebagri

src/Client.php

@@ -50,8 +50,8 @@ public function setHttpClient(?\GuzzleHttp\Client $httpClient = null): void
             'headers' => [
                 'Accept' => 'application/json',
                 'Content-Type' => 'application/json',
-                'Authorization' => 'Bearer ' . $this->token,
-                'User-Agent' => 'YourResellingClient/1.0'
+                'X-FIRE-APIKEY' => $this->token,
+                'User-Agent' => 'FireClient/1.0',
             ],
             'allow_redirects' => false,
             'timeout' => 120