Initialize culture settings in App.razor

Added dependency injection for `CultureService` in `App.razor` to dynamically initialize culture settings during the component's lifecycle.

Included `System.Globalization` and `EnvelopeGenerator.ReceiverUI.Services` namespaces to support culture-related functionality.

Injected `CultureService` and added an `OnInitializedAsync` method to set `CultureInfo.DefaultThreadCurrentCulture` and `CultureInfo.DefaultThreadCurrentUICulture` based on the service's initialization.

Reformatted surrounding `<Router>` code for clarity.

EnvelopeGenerator.ReceiverUI/App.razor

@@ -1,4 +1,8 @@
-<Router AppAssembly="@typeof(Program).Assembly">
+@using System.Globalization
+@using EnvelopeGenerator.ReceiverUI.Services
+@inject CultureService CultureService
+
+<Router AppAssembly="@typeof(Program).Assembly">
     <Found Context="routeData">
         <RouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
     </Found>
@@ -7,4 +11,13 @@
             <p>Sorry, there's nothing at this address.</p>
         </LayoutView>
     </NotFound>
-</Router>
+</Router>
+
+@code {
+    protected override async Task OnInitializedAsync()
+    {
+        var culture = await CultureService.InitializeCultureAsync();
+        CultureInfo.DefaultThreadCurrentCulture = culture;
+        CultureInfo.DefaultThreadCurrentUICulture = culture;
+    }
+}