feat: add getSystemStats method to retrieve system statistics

lib/src/_http_endpoints.dart

@@ -160,6 +160,13 @@ class ComfyApiHttpEndpoints {
     return jsonDecode(response.body);
   }
 
+  /// Gets system stats, including OS, Python version, etc.
+  Future<Map<String, dynamic>> getSystemStats() async {
+    final response = await _httpClient.get(Uri.parse('$host/system_stats'));
+    _validateResponse(response);
+    return jsonDecode(response.body);
+  }
+
   /// Gets a list of possible samplers from the object info
   Future<List<String>> getKSamplers() async {
     final objectInfo = await getObjectInfo();

lib/src/comfyui_api.dart

@@ -143,6 +143,10 @@ class ComfyUiApi {
   Future<Map<String, dynamic>> getObjectInfo() =>
       _httpEndpoints.getObjectInfo();
 
+  /// Gets system stats from the server
+  Future<Map<String, dynamic>> getSystemStats() =>
+      _httpEndpoints.getSystemStats();
+
   /// Gets a list of possible samplers from the object info
   Future<List<String>> getKSamplers() => _httpEndpoints.getKSamplers();