Add EnvelopeGenerator.ReceiverUI project and UI components

Introduced a new Razor Components-based web application, `EnvelopeGenerator.ReceiverUI`, to the solution. This includes:

- Added `EnvelopeGenerator.ReceiverUI` project to `EnvelopeGenerator.sln` with Debug and Release configurations.
- Created `EnvelopeGenerator.ReceiverUI.csproj` targeting `.NET 8.0` with nullable and implicit usings enabled.
- Added Razor components (`App.razor`, `Routes.razor`, `MainLayout.razor`, `NavMenu.razor`, `Counter.razor`, `Error.razor`, `Home.razor`, `Weather.razor`) for layout, navigation, and pages.
- Included styles (`MainLayout.razor.css`, `NavMenu.razor.css`, `app.css`) and assets (`favicon.png`, `bootstrap.min.css`).
- Configured logging and allowed hosts in `appsettings.json` and `appsettings.Development.json`.
- Added `Program.cs` to configure and run the application.
- Added `launchSettings.json` for development and debugging profiles.

These changes enable a modern, interactive web interface with Bootstrap styling and development-friendly configurations.

EnvelopeGenerator.ReceiverUI/Program.cs

@@ -0,0 +1,27 @@
+using EnvelopeGenerator.ReceiverUI.Components;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Add services to the container.
+builder.Services.AddRazorComponents()
+    .AddInteractiveServerComponents();
+
+var app = builder.Build();
+
+// Configure the HTTP request pipeline.
+if (!app.Environment.IsDevelopment())
+{
+    app.UseExceptionHandler("/Error", createScopeForErrors: true);
+    // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
+    app.UseHsts();
+}
+
+app.UseHttpsRedirection();
+
+app.UseStaticFiles();
+app.UseAntiforgery();
+
+app.MapRazorComponents<App>()
+    .AddInteractiveServerRenderMode();
+
+app.Run();