Fix signature field formatting and add text truncation

Address customer feedback on signature field layout issues:
- Added truncation logic in `PDFBurner.vb` to limit text length
  based on per-field maximums, appending a suffix (e.g., `..`).
- Enhanced `PDFBurnerParams.vb` with `TextMaxLengths` and
  `TruncationSuffix` for configurable truncation behavior.
- Improved spacing and layout handling for signature fields to
  prevent text collisions within fixed dimensions.
- Updated `EnvelopeGenerator.sln` with documentation for the
  signature formatting fix (`fix-signature-field-formatting.md`).
- Applied truncation consistently across `AddFormFieldValue`
  overloads and ensured deterministic rendering of annotations.

EnvelopeGenerator.CommonServices/Jobs/FinalizeDocument/PDFBurnerParams.vb

@@ -12,5 +12,23 @@ Namespace Jobs.FinalizeDocument
         Public Property FontSize As Integer = 8
 
         Public Property FontStyle As FontStyle = FontStyle.Italic
+
+        ''' <summary>
+        ''' The suffix appended to a truncated field value. Defaults to "..".
+        ''' Can be changed to any string (e.g. "…", "...", "").
+        ''' </summary>
+        Public Property TruncationSuffix As String = ".."
+
+        ''' <summary>
+        ''' Per-field maximum character count (including the TruncationSuffix).
+        ''' If a value exceeds the limit it is cut and TruncationSuffix is appended.
+        ''' Keys must match egName values used in PDFBurner (e.g. "name", "position", "city", "date").
+        ''' Set a value to 0 to disable truncation for that field.
+        ''' </summary>
+        Public Property TextMaxLengths As New Dictionary(Of String, Integer) From {
+            {"position", 20},
+            {"city", 20},
+            {"date", 28}
+        }
     End Class
 End Namespace