Routing Management and Creating NotFound Pages in Blazor

Blazor's route handling received significant improvements in .NET 10. The new `NotFoundPage` parameter on the `Router` component lets you specify a dedicated Razor component for 404 pages, replacing the previously broken `NotFound` render fragment. A custom `NotFoundContext` service can be registered to pass contextual headings and messages to the 404 page, enabling both generic and product-specific error messages. Combined with `NavigationManager.NotFound()` and `OnNotFound` (introduced in .NET 9), developers can trigger proper HTTP 404 responses with custom content. Additionally, .NET 10 allows inheriting from `NavLink` to write custom URL-matching logic, fixing the long-standing issue where active link highlighting was lost when navigating to child routes or URLs with query strings.