Add AtpResponseException for API error handling

src/Exceptions/AtpResponseException.php

···
+<?php
+
+namespace SocialDept\AtpClient\Exceptions;
+
+use Illuminate\Http\Client\Response;
+
+class AtpResponseException extends \Exception
+{
+    public function __construct(
+        public readonly string $errorCode,
+        public readonly string $errorMessage,
+        public readonly int $httpStatus,
+        public readonly string $endpoint,
+        public readonly array $responseBody,
+    ) {
+        parent::__construct("{$errorCode}: {$errorMessage}", $httpStatus);
+    }
+
+    public static function fromResponse(Response $response, string $endpoint): self
+    {
+        $body = $response->json() ?? [];
+
+        return new self(
+            errorCode: $body['error'] ?? 'UnknownError',
+            errorMessage: $body['message'] ?? $response->body(),
+            httpStatus: $response->status(),
+            endpoint: $endpoint,
+            responseBody: $body,
+        );
+    }
+}