Enhance grid UI and refactor boot overlay logic

- Updated `MappingProfile.cs` to add detailed mapping for `Envelope` to `EnvelopeDto`, including `EnvelopeTypeTitle`.
- Added a grid persistence hint banner in `EnvelopeSenderPage.razor` with an SVG icon and German message.
- Introduced three new columns (`EnvelopeTypeTitle`, `AddedWhen`, `ChangedWhen`) to the grid in `EnvelopeSenderPage.razor`.
- Refactored boot overlay removal logic in `App.razor` into a reusable function `sfRemoveBootOverlay`.
- Simplified event handling for overlay removal and fallback logic in `App.razor`.
- Adjusted `.sender-grid-wrapper` padding in `sender-page.css` and added styles for the new grid persistence hint banner.

EnvelopeGenerator.Application/Common/MappingProfile.cs

@@ -28,7 +28,9 @@ public class MappingProfile : Profile
         CreateMap<DocReceiverElement, DocReceiverElementDto>();
         CreateMap<DocumentStatus, DocumentStatusDto>();
         CreateMap<EmailTemplate, EmailTemplateDto>();
-        CreateMap<Envelope, EnvelopeDto>();
+        CreateMap<Envelope, EnvelopeDto>()
+            .ForMember(dest => dest.EnvelopeTypeTitle,
+                       opt  => opt.MapFrom(src => src.Type != null ? src.Type.Title : null));
         CreateMap<Document, DocumentDto>();
         CreateMap<History, HistoryDto>().ForMember(dest => dest.ActionDate, opt => opt.MapFrom(src => src.ChangedWhen));
         CreateMap<History, HistoryCreateDto>().ForMember(dest => dest.ActionDate, opt => opt.MapFrom(src => src.ChangedWhen));