feat(Program): make Quartz cron schedule configurable via appsettings

- Replaced hardcoded cron expression with configuration-based `Worker:CronExpression`.
- Throws descriptive exception if cron expression is missing.
- Keeps previous worker and DB context setup unchanged.

EnvelopeGenerator.Finalizer/Models/WorkerOptions.cs

@@ -1,19 +0,0 @@
-namespace EnvelopeGenerator.Finalizer.Models;
-
-public class WorkerOptions
-{
-    private double _intervalInMin = 1.0;
-
-    public double IntervalInMin { 
-        get => _intervalInMin; 
-        set 
-        {
-            _intervalInMin = value;
-            IntervalInMillisecond = Min2Millisecond(value);
-        } 
-    }
-
-    public int IntervalInMillisecond { get; private set; } = Min2Millisecond(1.0);
-
-    private static int Min2Millisecond(double min) => Convert.ToInt32(Math.Round(min * 60 * 1000));
-}