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

@@ -0,0 +1,39 @@
+@page "/leverandoerer"
+@model PlanTempus.Application.Features.Suppliers.Pages.IndexModel
+@{
+    ViewData["Title"] = "Leverandører";
+}
+
+<swp-sticky-header>
+    <swp-header-content>
+        <swp-page-header>
+            <swp-page-title>
+                <h1 localize="suppliers.title">Leverandører</h1>
+                <p localize="suppliers.subtitle">Administrer leverandører og indkøb</p>
+            </swp-page-title>
+        </swp-page-header>
+
+        <swp-stats-row class="cols-4">
+            <swp-stat-card class="highlight">
+                <swp-stat-value>12</swp-stat-value>
+                <swp-stat-label localize="suppliers.stats.total">Leverandører i alt</swp-stat-label>
+            </swp-stat-card>
+            <swp-stat-card>
+                <swp-stat-value>10</swp-stat-value>
+                <swp-stat-label localize="suppliers.stats.active">Aktive</swp-stat-label>
+            </swp-stat-card>
+            <swp-stat-card>
+                <swp-stat-value>45.230 kr</swp-stat-value>
+                <swp-stat-label localize="suppliers.stats.purchasesThisMonth">Indkøb denne måned</swp-stat-label>
+            </swp-stat-card>
+            <swp-stat-card class="warning">
+                <swp-stat-value>3</swp-stat-value>
+                <swp-stat-label localize="suppliers.stats.pendingOrders">Afventende ordrer</swp-stat-label>
+            </swp-stat-card>
+        </swp-stats-row>
+    </swp-header-content>
+</swp-sticky-header>
+
+<swp-page-container>
+    @await Component.InvokeAsync("SupplierTable")
+</swp-page-container>