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/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}