Add a loading animation for file uploads

[isaachili]

Large files may take some time to process and thus, it would be beneficial for the user to introduce a loading animation; otherwise, the user might think that the application has crashed.

[isaachili]

.NET 8 Blazor WASM does not support multi-threading:
dotnet/aspnetcore#54365
dotnet/aspnetcore#17730

[isaachili]

Attempted to use Task.Delay(TimeSpan.FromMilliseconds(1)) to yield back to the current context and thus, allowing the UI to update. The UI experienced no noticeable freezing; however, it significantly prolonged the process time.

A more conservative Task.Delay(TimeSpan.FromMicroseconds(100)) yields no benefits in terms of UI — the UI experienced frequent freezing.

Task.Yield() had no impact on UI performance either.

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It could be worth looking into incorporating Web Workers with WASM to offload the work to a background thread.