Adds suppliers feature to application

Introduces comprehensive suppliers management with mock data, localization, and UI components

Implements:
- Suppliers page with data table
- Localization for Danish and English
- Search and filtering functionality
- Responsive table design
- Mock data for initial population

PlanTempus.Application/Features/Suppliers/Pages/Index.cshtml.cs

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