docs: show todo.done in useImmer checkbox example

[Hashim1999164]

Summary

• Fixes [docs] [examples] useImmer To-do list example is using wrong object property for checked #1011 by completing the useImmer todo list example with the correct checked={todo.done} binding
• Removes the broken CodeSandbox link that used todo.finished while state objects use done
• Updates both English and zh-CN docs pages

Test plan

• Verified the example uses todo.done consistently for state updates and checkbox checked
• Confirmed no other doc references to the outdated CodeSandbox remain on this page