Added a null check in `EnvelopeReceiverPage.razor` to log a warning when `_envelopeReceiver` is null. Updated `ReportViewer.razor` to wrap `EnvelopeReceiverService.GetAsync` in a `try-catch` block, logging `HttpRequestException` errors and allowing the UI to handle null values gracefully.
Enhanced `EnvelopeReceiverService.GetAsync` to throw detailed `HttpRequestException` on API failures, including status code and reason phrase. Added `using System.Net;` to support HTTP-related classes. Updated method documentation to reflect the new behavior.
These changes improve error diagnostics, logging, and maintainability across the codebase.
Introduced `EnvelopeReceiverDto` and its nested models (`EnvelopeClientDto`, `EnvelopeSenderDto`, `DocumentClientDto`, `SignatureClientDto`, `ReceiverClientDto`) to represent client-side data for envelope receivers and their associated entities.
Added `EnvelopeReceiverService` to fetch `EnvelopeReceiverDto` from the API using `HttpClient`. Implemented error handling and JSON deserialization with `JsonSerializerDefaults.Web`. Updated necessary `using` directives.
