allow vorgangPIN to be changed on Vorgang page

includes:
- UI and backend logic
- adjustment to `NameItemEditor` to disallow deletion

src/lib/components/NameItemEditor.svelte

@@ -15,7 +15,7 @@
 	export let currentName: string;
 	export let vorgangToken: string | null;
 	export let onSave: (n: string, o: string, t?: string) => unknown = () => {};
-	export let onDelete: (n: string) => unknown = () => {};
+	export let onDelete: (n: string) => unknown | null = () => {};
 
 	let localName = currentName;
 	let isEditing = false;
@@ -98,13 +98,15 @@
       >
         <Edit class="w-4 h-4" />
       </button>
-      <button
-        data-testid="delete-button"
-        onclick={handleDeleteClick}
-        class="text-gray-500 hover:text-red-600 transition"
-      >
-        <Trash class="w-4 h-4" />
-      </button>
+      {#if onDelete}
+		<button
+			data-testid="delete-button"
+			onclick={handleDeleteClick}
+			class="text-gray-500 hover:text-red-600 transition"
+		>
+			<Trash class="w-4 h-4" />
+		</button>
+      {/if}
     </div>
   {/if}