Improve signature UI and refactor ReportViewer.razor

Updated the signature button text and SVG icon for clarity.
Enhanced the `DxPopup` component with better interaction
properties (`CloseOnEscape` and `CloseOnOutsideClick`).
Disabled the "Close" button in the popup when no signature
is captured.

Reformatted and restructured constants and fields in the
`@code` block for readability. Reintroduced previously
removed fields, constants, and methods to ensure
functionality. Added a conditional block in `LogoutAsync`
to open the signature popup when the user has access.

Performed general cleanup and code reorganization to
improve maintainability.

EnvelopeGenerator.ReceiverUI/Pages/ReportViewer.razor

@@ -54,7 +54,7 @@
                     </svg>
                     <span>Unterschrift gespeichert</span>
                 } else {
-                    <span>Unterschrift erstellen</span>
+                    <span>Unterschrift &auml;ndern</span>
                 }
             </button>
             @if (_annotations.Count > 0) {
@@ -160,7 +160,7 @@
         <div class="d-flex gap-2 flex-wrap justify-content-end w-100">
             <button class="btn btn-outline-secondary" @onclick="RenewSignatureAsync">Unterschrift erneuern</button>
             <button class="btn btn-primary" @onclick="SaveSignatureAsync">Speichern</button>
-            <button class="btn btn-secondary" @onclick="CloseSignaturePopup">Schliessen</button>
+            <button class="btn btn-secondary" @onclick="CloseSignaturePopup" disabled="@(_capturedSignature is null)">Schliessen</button>
         </div>
     </FooterContentTemplate>
 </DxPopup>
@@ -233,6 +233,10 @@ int _lastOverlayViewerKey = -1;
                 Navigation.NavigateTo($"/login/{Uri.EscapeDataString(EnvelopeKey)}");
                 return;
             }
+            else
+            {
+                await OpenSignaturePopupAsync();
+            }
         }
 
         _annotations = await AnnotationService.GetAnnotationsAsync(EnvelopeKey ?? "fake");