fix(auth): detect banned/deleted user on page load via InitializeAsync

- LoginService.InitializeAsync: after fetching LoggedUser, check IsBanned
  and DeletedAt. If banned/disabled, set ForceLogoutReason, call Logout
  to clear state, and return false
- App.razor: after InitializeAsync completes, check ForceLogoutReason
  and navigate to /login if set. This handles the timing issue where
  MainLayout isnt created yet when the event fires on page load

Refs #45

MilkStream.Client/Components/App.razor

@@ -1,4 +1,5 @@
 @inject LoginService loginService
+@inject NavigationManager NavigationManager
 
 @if (_initialized) {
     <Router AppAssembly="typeof(Program).Assembly">
@@ -20,5 +21,8 @@
     protected override async Task OnInitializedAsync() {
         await loginService.InitializeAsync();
         _initialized = true;
+
+        if (loginService.ForceLogoutReason != null)
+            NavigationManager.NavigateTo("/login", true);
     }
 }

MilkStream.Client/Services/LoginService.cs

@@ -112,6 +112,19 @@ public sealed class LoginService : ServiceBase {
 
         AuthInfo   = auth;
         LoggedUser = await FetchLoggedUserAsync();
+
+        if (LoggedUser is { IsBanned: true }) {
+            ForceLogoutReason = "User is banned";
+            await Logout();
+            return false;
+        }
+
+        if (LoggedUser is { DeletedAt: not null }) {
+            ForceLogoutReason = "User is disabled";
+            await Logout();
+            return false;
+        }
+
         return IsLoggedIn;
     }