add ai integration examples for scheduler, grid, editor, and chart te…

[antonmironovv]

…lerik/kendo#24269

[eyupyusein]

1. Consider adding try/catch clause to ProcessAsync, too.
2. In the Controllers, there is repeating code in the Actions - you can extract it to a common Method, e.g.:

                _http.DefaultRequestHeaders.Clear();
                _http.DefaultRequestHeaders.Add("api-key", _apiKey);

                var content = new StringContent(JsonConvert.SerializeObject(payload), Encoding.UTF8, "application/json");
                var response = await _http.PostAsync(url, content);
                var text = await response.Content.ReadAsStringAsync();

                if (!response.IsSuccessStatusCode)
                    return $"Azure OpenAI API error: {response.StatusCode}";

                var json = JObject.Parse(text);
                return json["choices"]?[0]?["message"]?["content"]?.ToString()?.Trim() ??