feat: Add health check monitoring for ProfileWorker

ProfileWorker changes:
- Implement IHealthCheck interface
- Replace _workCount with DateTime-based tracking
- Track _lastSuccessfulRun, _consecutiveFailures, _lastException
- Graceful shutdown handling (OperationCanceledException)
- Health states: Healthy, Degraded (1-2 failures), Unhealthy (3x interval)

DependencyInjection changes:
- Register ProfileWorker as singleton (for health check access)
- Use factory pattern for IHostedService registration

Program.cs changes:
- Add health check service with ProfileWorker
- Map /health endpoint (full JSON response with all checks)
- Map /health/ready endpoint (filtered by 'ready' tag)
- Custom JSON response writer with detailed metrics

ECMJobRunner.WebCron/Program.cs

@@ -101,6 +101,10 @@ builder.Services.AddHangfireServer();
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
 
+// Add health checks
+builder.Services.AddHealthChecks()
+    .AddCheck<ProfileWorker>("profile-worker", tags: new[] { "ready", "worker" });
+
 // Add Serilog.UI with SQLite provider - use same path from configuration
 var serilogUiLogDirectory = builder.Configuration.GetValue<string>("Application:LogDirectory")
     ?? throw new InvalidOperationException("Application:LogDirectory not found in configuration.");
@@ -139,6 +143,36 @@ app.UseSerilogUi();
 
 app.MapControllers();
 
+// Map health check endpoints
+app.MapHealthChecks("/health", new Microsoft.AspNetCore.Diagnostics.HealthChecks.HealthCheckOptions
+{
+    Predicate = _ => true,
+    ResponseWriter = async (context, report) =>
+    {
+        context.Response.ContentType = "application/json";
+        var result = System.Text.Json.JsonSerializer.Serialize(new
+        {
+            status = report.Status.ToString(),
+            timestamp = DateTime.UtcNow,
+            checks = report.Entries.Select(e => new
+            {
+                name = e.Key,
+                status = e.Value.Status.ToString(),
+                description = e.Value.Description,
+                duration = e.Value.Duration.TotalMilliseconds,
+                exception = e.Value.Exception?.Message,
+                data = e.Value.Data
+            })
+        });
+        await context.Response.WriteAsync(result);
+    }
+});
+
+app.MapHealthChecks("/health/ready", new Microsoft.AspNetCore.Diagnostics.HealthChecks.HealthCheckOptions
+{
+    Predicate = check => check.Tags.Contains("ready")
+});
+
 // Redirect root path to Hangfire dashboard
 app.MapGet("/", () => Results.Redirect("/hangfire"));