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/Pages/Index.cshtml.cs

@@ -0,0 +1,10 @@
+using Microsoft.AspNetCore.Mvc.RazorPages;
+
+namespace PlanTempus.Application.Features.Account.Pages;
+
+public class IndexModel : PageModel
+{
+    public void OnGet()
+    {
+    }
+}