fix(portal): add Authorization namespace to _Imports.razor

Without @using Microsoft.AspNetCore.Components.Authorization in _Imports.razor,
the <CascadingAuthenticationState> tag in App.razor was silently compiled as
an HTML element instead of a Blazor component. This left AuthorizeView with
no cascading Task<AuthenticationState>, causing every circuit to crash with
"Authorization requires a cascading parameter of type Task<AuthenticationState>".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: aurelianware

src/portal/CloudHealthOffice.Portal/_Imports.razor

@@ -1,5 +1,6 @@
 @using System.Net.Http
 @using System.Net.Http.Json
+@using Microsoft.AspNetCore.Components.Authorization
 @using Microsoft.AspNetCore.Components.Forms
 @using Microsoft.AspNetCore.Components.Routing
 @using Microsoft.AspNetCore.Components.Web