feat(FinishEnvelopeJob): enhance FinishEnvelopeJob to fetch signed envelopes

- Added MediatR dependency to query envelopes
- Injected GdPictureOptions via IOptions
- Updated Execute method to fetch envelopes with status 'EnvelopeCompletelySigned'
- Preserved logging with job details
- Prepared loop for further processing of envelopes

EnvelopeGenerator.Finalizer/Job/EnvelopeTaskApiJob.cs

@@ -15,7 +15,7 @@ namespace EnvelopeGenerator.Finalizer.Job
         {
             if (_logger.IsEnabled(LogLevel.Information))
             {
-                _logger.LogInformation("{jobName} running at: {time}", GetType().FullName, DateTimeOffset.Now);
+                _logger.LogInformation("{jobName} running at: {time}", context.JobDetail.Key, DateTimeOffset.Now);
             }
 
             return Task.CompletedTask;