Restructure into feature folders with code-behind and scoped CSS

Elternbeirat.Web/_Imports.razor

@@ -0,0 +1,10 @@
+@using System.Net.Http
+@using System.Net.Http.Json
+@using Microsoft.AspNetCore.Components.Forms
+@using Microsoft.AspNetCore.Components.Routing
+@using Microsoft.AspNetCore.Components.Web
+@using static Microsoft.AspNetCore.Components.Web.RenderMode
+@using Microsoft.AspNetCore.Components.Web.Virtualization
+@using Microsoft.JSInterop
+@using Elternbeirat.Web
+@using Elternbeirat.Web.Services