fix(search-filter-bar): wait for slide transition before clicking undated toggle

track_reactivity_loss in Svelte 5 async.js fires when a $bindable write
happens while the slide transition is still being tracked asynchronously.
Waiting for the toggle to be visible ensures the transition has settled.

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

frontend/src/routes/SearchFilterBar.svelte.spec.ts

@@ -132,6 +132,9 @@ describe('SearchFilterBar – undated-only toggle (#668)', () => {
 	async function openAdvanced() {
 		const filterBtn = page.getByRole('button', { name: 'Filter', exact: true });
 		await filterBtn.click();
+		// Wait for slide transition to finish before interacting with contents —
+		// clicking during the transition triggers track_reactivity_loss in Svelte 5 async.js
+		await expect.element(page.getByTestId('undated-only-toggle')).toBeVisible();
 	}
 
 	it('renders the "Nur undatierte" toggle in the advanced row', async () => {