refactor(geschichte): extract delete handler to [id]/+page.svelte, pass via ondelete prop

Moves the confirm-then-delete flow out of StoryReader and JourneyReader into
the single [id]/+page.svelte owner. Both reader components gain an optional
ondelete prop — the delete button calls ondelete?.() so the handler is opt-in
and never duplicated. Tests verify the prop is called on click.

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

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

@@ -1,6 +1,6 @@
-import { describe, it, expect, afterEach } from 'vitest';
+import { describe, it, expect, vi, afterEach } from 'vitest';
 import { cleanup, render } from 'vitest-browser-svelte';
-import { page } from 'vitest/browser';
+import { page, userEvent } from 'vitest/browser';
 import { createConfirmService, CONFIRM_KEY } from '$lib/shared/services/confirm.svelte.js';
 import type { components } from '$lib/generated/api';
 
@@ -75,8 +75,11 @@ describe('JourneyReader', () => {
 			props: { geschichte: baseGeschichte({ body: '   ' }), canBlogWrite: false }
 		});
 
-		expect(document.body.textContent?.trim().replace(/\s+/g, ' ')).not.toContain('    ');
+		// Whitespace-only body must NOT produce a visible intro paragraph.
+		// The only rendered content should be the empty-state message.
 		await expect.element(page.getByTestId('journey-empty-state')).toBeVisible();
+		const paragraphs = document.querySelectorAll('p:not([data-testid])');
+		expect(paragraphs.length).toBe(0);
 	});
 
 	it('renders empty-state message when items array is empty', async () => {
@@ -148,6 +151,22 @@ describe('JourneyReader', () => {
 		await expect.element(page.getByText('Diese Lesereise ist noch leer.')).not.toBeInTheDocument();
 	});
 
+	it('clicking delete button calls ondelete prop', async () => {
+		const ondelete = vi.fn().mockResolvedValue(undefined);
+		render(JourneyReader, {
+			context: ctx(),
+			props: {
+				geschichte: baseGeschichte({ items: [docItem('i1', 'Brief', 0)] }),
+				canBlogWrite: true,
+				ondelete
+			}
+		});
+
+		await userEvent.click(page.getByRole('button', { name: /löschen/i }));
+
+		expect(ondelete).toHaveBeenCalledOnce();
+	});
+
 	it('XSS: Journey body is rendered as plaintext — injected payload does not execute', async () => {
 		// JourneyReader uses Svelte text interpolation, NOT {@html}.
 		render(JourneyReader, {