Adds account management and subscription features

Introduces new account pages for managing subscriptions, payment methods, and invoice history

Includes:
- Subscription plan selection view
- Payment method display component
- Invoice history table
- Account page layout and styling

Updates main layout to include new CSS files for account management

PlanTempus.Application/Features/Account/Components/InvoiceHistory/InvoiceHistoryViewComponent.cs

@@ -0,0 +1,15 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace PlanTempus.Application.Features.Account.Components;
+
+/// <summary>
+/// ViewComponent for the invoice history table.
+/// Shows past invoices with status and download options.
+/// </summary>
+public class InvoiceHistoryViewComponent : ViewComponent
+{
+    public IViewComponentResult Invoke()
+    {
+        return View();
+    }
+}