Test Persistence End to End

Use the browser to verify that persistence works through the full workflow.

1. Add several tasks.
2. Set different due dates and priorities.
3. Complete one task.
4. Edit another task.
5. Delete a task.
6. Reload the page.
7. Confirm that the remaining tasks still have the correct details and states.

If something resets, find the operation that changed the task data and make sure it calls saveTasks() afterward.

Checkpoint: Refreshing the page no longer clears the application data.