Introduced a new Blazor WebAssembly project (`EnvelopeGenerator.WebUI.Client`) targeting .NET 8.0 for client-side functionality.
Added a Blazor Server project (`EnvelopeGenerator.WebUI`) to host the application and enable server-side rendering.
Created essential Razor components (`MainLayout.razor`, `Home.razor`, `Routes.razor`, `Error.razor`, etc.) for layouts, routing, and error handling.
Configured project files, solution structure, and build settings. Added necessary styles, app settings, and launch profiles for development.
