fix(journey-editor): render empty-state message when items list is empty

Previously the item list area was blank when no items had been added.
The empty-state paragraph uses the existing journey_empty_state i18n key.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/geschichte/JourneyEditor.svelte

@@ -244,6 +244,9 @@ async function save(nextStatus: 'DRAFT' | 'PUBLISHED') {
 			onpointerup={() => dragDrop.handlePointerUp()}
 			class="flex flex-col gap-2"
 		>
+			{#if items.length === 0}
+				<p class="font-sans text-sm text-ink-3">{m.journey_empty_state()}</p>
+			{/if}
 			{#each items as item, i (item.id)}
 				<!-- svelte-ignore a11y_no_static_element_interactions -->
 				<div

frontend/src/lib/geschichte/JourneyEditor.svelte.spec.ts

@@ -55,6 +55,11 @@ describe('JourneyEditor — empty state', () => {
 		render(JourneyEditor, defaultProps());
 		await expect.element(page.getByRole('button', { name: /Veröffentlichen/ })).toBeDisabled();
 	});
+
+	it('shows empty state message when items list is empty', async () => {
+		render(JourneyEditor, defaultProps());
+		await expect.element(page.getByText('Diese Lesereise ist noch leer.')).toBeInTheDocument();
+	});
 });
 
 describe('JourneyEditor — items in position order', () => {