Refactor signature popup handling in ReportViewer

Simplified the `OpenSignaturePopupAsync` method by converting it to a synchronous `void` method and removing unnecessary asynchronous calls. Introduced a new `OnPopupShownAsync` method to handle popup initialization logic.

Updated the `<Popup>` component to include the `Shown="OnPopupShownAsync"` attribute and re-added the `CloseOnOutsideClick="false"` attribute. Improved the logic for opening the signature popup by setting the active tab and resetting validation messages inline.

Enhanced the `OnAfterRenderAsync` lifecycle method to include additional checks for `Report`, annotations, and signature state before triggering JavaScript runtime calls. These changes improve the popup's behavior and overall state management.

EnvelopeGenerator.ReceiverUI/Pages/ReportViewer.razor

@@ -96,7 +96,8 @@ Width="620px"
 ShowFooter="true"
 CloseOnEscape="false"
 ShowCloseButton="false"
-CloseOnOutsideClick="false">
+CloseOnOutsideClick="false"
+Shown="OnPopupShownAsync">
     <BodyContentTemplate>
         <ul class="nav nav-tabs mb-3">
             <li class="nav-item">
@@ -235,7 +236,10 @@ CloseOnOutsideClick="false">
             }
             else
             {
-                await OpenSignaturePopupAsync();
+                ActiveSignatureTab = SignatureTabDraw;
+                SignaturePopupVisible = true;
+                SignatureValidationMessage = null;
+                PopupValidationMessage = null;
             }
         }
 
@@ -255,6 +259,7 @@ CloseOnOutsideClick="false">
         if (firstRender)
             _dotNetRef = DotNetObjectReference.Create(this);
 
+
         if (Report is not null && _annotations.Count > 0
             && _capturedSignature is not null && !SignatureApplied
             && _lastOverlayViewerKey != ViewerKey) {
@@ -274,13 +279,14 @@ CloseOnOutsideClick="false">
         await InvokeAsync(StateHasChanged);
     }
 
-    async Task OpenSignaturePopupAsync() {
+    void OpenSignaturePopupAsync() {
         ActiveSignatureTab = SignatureTabDraw;
         SignaturePopupVisible = true;
         SignatureValidationMessage = null;
         PopupValidationMessage = null;
-        await InvokeAsync(StateHasChanged);
-        await Task.Delay(50);
+    }
+
+    async Task OnPopupShownAsync() {
         await InitializeActiveSignatureTabAsync();
     }