Show only one "File transfer complete" pop up window

Right now if you upload multiple files at a time, it will show this pop up for each file transferred. It should only show it once, either at the beginning or the end of the transfer.

No file or test is named in the issue. Start by locating the Blazor UI code that displays the "File transfer complete" notification and trace how notifications are triggered for multi-file uploads. Done means one notification appears for the whole transfer rather than one per file.

Written by the indexing model from the issue text.