Refactor. Add data layer

BudgetApp/Components/ToastContainer.razor

@@ -3,49 +3,11 @@
 @rendermode InteractiveServer
 
 <div class="toast-stack">
-    @foreach (var toast in toasts)
+    @foreach (var toast in _toasts)
     {
         <div class="toast-item @(toast.Dismissing ? "toast-dismiss" : "")">
             <span class="toast-icon">⚠</span>
             <span class="toast-message">@toast.Message</span>
         </div>
     }
-</div>
-
-@code {
-    private readonly List<ToastItem> toasts = [];
-
-    protected override void OnInitialized()
-    {
-        ToastService.OnShow += ShowToast;
-    }
-
-    private async void ShowToast(string message)
-    {
-        var toast = new ToastItem { Message = message };
-        toasts.Add(toast);
-        await InvokeAsync(StateHasChanged);
-        _ = DismissAfterDelay(toast);
-    }
-
-    private async Task DismissAfterDelay(ToastItem toast)
-    {
-        await Task.Delay(3500);
-        toast.Dismissing = true;
-        await InvokeAsync(StateHasChanged);
-        await Task.Delay(300);
-        toasts.Remove(toast);
-        await InvokeAsync(StateHasChanged);
-    }
-
-    public void Dispose()
-    {
-        ToastService.OnShow -= ShowToast;
-    }
-
-    private sealed class ToastItem
-    {
-        public string Message { get; set; } = "";
-        public bool Dismissing { get; set; }
-    }
-}
+</div>