Add Kaigen API health check and configuration

- Introduced Kaigen configuration section in appsettings.Oda.json with BaseUrl.
- Added HTTP client for Kaigen API health check in Program.cs.
- Registered KaigenHealthCheck service for monitoring Kaigen API connectivity.

src/Managing.Api/HealthChecks/KaigenHealthCheck.cs

@@ -0,0 +1,94 @@
+using System.Text.Json;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace Managing.Api.HealthChecks
+{
+    public class KaigenHealthCheck : IHealthCheck
+    {
+        private readonly HttpClient _httpClient;
+        private readonly string _kaigenBaseUrl;
+
+        public KaigenHealthCheck(IHttpClientFactory httpClientFactory, string kaigenBaseUrl)
+        {
+            _httpClient = httpClientFactory.CreateClient("KaigenHealthCheck");
+            _kaigenBaseUrl = kaigenBaseUrl;
+        }
+
+        public async Task<HealthCheckResult> CheckHealthAsync(HealthCheckContext context,
+            CancellationToken cancellationToken = default)
+        {
+            try
+            {
+                var response = await _httpClient.GetAsync($"{_kaigenBaseUrl}/api/health", cancellationToken);
+
+                if (!response.IsSuccessStatusCode)
+                {
+                    return HealthCheckResult.Degraded(
+                        $"Kaigen API health check failed with status code: {response.StatusCode}",
+                        data: new Dictionary<string, object>
+                        {
+                            ["StatusCode"] = (int)response.StatusCode,
+                            ["Endpoint"] = $"{_kaigenBaseUrl}/api/health"
+                        });
+                }
+
+                var content = await response.Content.ReadAsStringAsync(cancellationToken);
+
+                // Parse the JSON response to extract the detailed data
+                using (JsonDocument document = JsonDocument.Parse(content))
+                {
+                    var root = document.RootElement;
+                    string status = "OK";
+                    string message = "Server is healthy";
+
+                    if (root.TryGetProperty("status", out var statusElement))
+                    {
+                        status = statusElement.GetString();
+                    }
+
+                    if (root.TryGetProperty("message", out var messageElement))
+                    {
+                        message = messageElement.GetString();
+                    }
+
+                    // Extract the detailed data from the Kaigen response
+                    var data = new Dictionary<string, object>();
+
+                    // Parse timestamp if available
+                    if (root.TryGetProperty("timestamp", out var timestampElement))
+                    {
+                        data["timestamp"] = timestampElement.GetString();
+                    }
+
+                    data["message"] = message;
+
+                    // Determine overall health result based on status
+                    if (status.ToUpper() == "OK")
+                    {
+                        return HealthCheckResult.Healthy(
+                            "Kaigen API is healthy",
+                            data: data);
+                    }
+                    else
+                    {
+                        return HealthCheckResult.Unhealthy(
+                            $"Kaigen API returned status: {status}",
+                            data: data);
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                return HealthCheckResult.Unhealthy(
+                    "Failed to connect to Kaigen API",
+                    ex,
+                    data: new Dictionary<string, object>
+                    {
+                        ["Endpoint"] = $"{_kaigenBaseUrl}/api/health",
+                        ["ErrorMessage"] = ex.Message,
+                        ["ErrorType"] = ex.GetType().Name
+                    });
+            }
+        }
+    }
+}