Add job framework for envelope processing and PDF finalization

Introduced new job classes for envelope processing and document finalization, including APIEnvelopeJob and FinalizeDocumentJob, both implementing Quartz IJob. Added supporting utilities for PDF annotation burning (PDFBurner), PDF merging (PDFMerger), and report generation (ReportCreator), along with related data models and exception types. Updated project references and dependencies to support Quartz scheduling, SQL Server access, and PDF manipulation with iText. This establishes a modular, extensible job-processing framework for envelope management and reporting.

EnvelopeGenerator.Jobs/Jobs/DataRowExtensions.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Data;
+
+namespace EnvelopeGenerator.CommonServices.Jobs;
+
+public static class DataRowExtensions
+{
+    public static T? GetValueOrDefault<T>(this DataRow row, string columnName, T? defaultValue = default)
+    {
+        if (!row.Table.Columns.Contains(columnName))
+        {
+            return defaultValue;
+        }
+
+        var value = row[columnName];
+        if (value == DBNull.Value)
+        {
+            return defaultValue;
+        }
+
+        try
+        {
+            return (T)Convert.ChangeType(value, typeof(T));
+        }
+        catch
+        {
+            return defaultValue;
+        }
+    }
+}