refactor(notification-tests): use vi.mocked instead of type cast in call-order test

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

frontend/src/lib/notification/NotificationDropdown.svelte.test.ts

@@ -193,7 +193,7 @@ describe('NotificationDropdown', () => {
 	it('calls onClose before navigating to /aktivitaeten', async () => {
 		const callOrder: string[] = [];
 		const onClose = vi.fn(() => callOrder.push('close'));
-		(goto as ReturnType<typeof vi.fn>).mockImplementation(() => callOrder.push('goto'));
+		vi.mocked(goto).mockImplementation(() => callOrder.push('goto'));
 		render(NotificationDropdown, {
 			props: {
 				notifications: [],