refactor: wrap repository access in a DI scope in PDFBurner

- Updated `BurnAnnotsToPDF` to create a scope using `Factory.Shared.ScopeFactory.CreateScope()`
  before accessing the `Signature` repository.
- Ensures proper disposal of services and improves dependency injection usage.
- No functional changes to PDF burning logic.

EnvelopeGenerator.CommonServices/Jobs/FinalizeDocument/PDFBurner.vb

@@ -36,7 +36,8 @@ Namespace Jobs.FinalizeDocument
 #Region "Burn PDF"
         Public Function BurnAnnotsToPDF(pSourceBuffer As Byte(), pInstantJSONList As List(Of String), envelopeId As Integer) As Byte()
             'read the elements of envelope with their annotations
-            Dim sigRepo = Factory.Shared.Repository(Of Signature)()
+            Using scope = Factory.Shared.ScopeFactory.CreateScope()
+                Dim sigRepo = scope.ServiceProvider.Repository(Of Signature)()
                 Dim elements = sigRepo _
                     .Where(Function(sig) sig.Document.EnvelopeId = envelopeId) _
                     .Include(Function(sig) sig.Annotations) _
@@ -45,6 +46,7 @@ Namespace Jobs.FinalizeDocument
                 Return If(elements.Any(),
                        BurnElementAnnotsToPDF(pSourceBuffer, elements),
                        BurnInstantJSONAnnotsToPDF(pSourceBuffer, pInstantJSONList))
+            End Using
         End Function
 
         Public Function BurnElementAnnotsToPDF(pSourceBuffer As Byte(), elements As List(Of Signature)) As Byte()