feat: Add edit and delete functionality for Verwaltungskosten

- Add verwaltungskosten_delete view with confirmation page
- Add delete URL route and template
- Fix template action buttons to use proper URLs for edit/delete
- Include audit logging for deletions
- Add comprehensive delete confirmation with entry details
- Remove non-functional details button from action group

app/stiftung/urls.py

@@ -219,6 +219,11 @@ urlpatterns = [
         views.verwaltungskosten_edit,
         name="verwaltungskosten_edit",
     ),
+    path(
+        "geschaeftsfuehrung/verwaltungskosten/<uuid:pk>/loeschen/",
+        views.verwaltungskosten_delete,
+        name="verwaltungskosten_delete",
+    ),
     path(
         "verwaltungskosten/mark-paid/",
         views.mark_expense_paid,