Set ViewData["ReadAndConfirm"] for envelope read-only state

Added "ReadAndConfirm" to ViewData, passing the envelope's ReadOnly property to the "ShowEnvelope" view. This enables the view to adjust its behavior or UI based on whether the envelope is read-only.

EnvelopeGenerator.Web/Controllers/EnvelopeController.cs

@@ -262,6 +262,8 @@ public class EnvelopeController : ViewControllerBase
 
         await HttpContext.SignInEnvelopeAsync(er, ReceiverRole.FullyAuth);
 
+        ViewData["ReadAndConfirm"] = er.Envelope.ReadOnly;
+
         //add PSPDFKit licence key
         ViewData["PSPDFKitLicenseKey"] = _configuration["PSPDFKitLicenseKey"];