restoreItem
Restores the value associated with a key in secure storage. This is useful if the value was previously removed using removeItem and needs to be retrieved again. Note that restoring a value is only possible if it hasn't been overwritten by a new value for the same key.
Parameters
key
The key to restore the value for.
callback
A callback function that is called when the operation is complete. The first argument is an error object, if any, and the second argument is the restored value, or null if the key is not found or cannot be restored.