Blazor UI: create ViewBase class and code behind

[ekolis]

What needs to be cleaned up?

The various Blazor views have a lot of duplicate code. Move it into a ViewBase class, and also move any C# code possible from the razor file to a razor.cs file for each view.

How will this benefit us?

Better organization, less duplicate code

What potential drawbacks are there to making this change?

Splitting code into multiple files could potentially make things a bit harder to find

Related issues

Parent of this is #309