Make worker delay configurable via appsettings.json

Refactored Worker to accept IConfiguration and read the delay interval from "Worker:DelayMilliseconds" in appsettings.json, replacing the previously hardcoded value. This allows the worker execution interval to be configured without code changes. Added a minimum delay safeguard and updated appsettings.json accordingly.

EnvelopeGenerator.ServiceHost/Worker.cs

@@ -3,10 +3,12 @@ namespace EnvelopeGenerator.ServiceHost;
 public class Worker : BackgroundService
 {
     private readonly ILogger<Worker> _logger;
+    private readonly int _delayMilliseconds;
 
-    public Worker(ILogger<Worker> logger)
+    public Worker(ILogger<Worker> logger, IConfiguration configuration)
     {
         _logger = logger;
+        _delayMilliseconds = Math.Max(1, configuration.GetValue("Worker:DelayMilliseconds", 1000));
     }
 
     protected override async Task ExecuteAsync(CancellationToken stoppingToken)
@@ -17,7 +19,7 @@ public class Worker : BackgroundService
             {
                 _logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
             }
-            await Task.Delay(1000, stoppingToken);
+            await Task.Delay(_delayMilliseconds, stoppingToken);
         }
     }
 }