* BaseDialog: fix documentation, and make `onFinished` optional
Since `onFinished` isn't used if `hasCancel` is false, it's a bit silly to make
it mandatory.
* AccessSecretStorageDialog: fix inability to enter recovery key
Wrap AccessSecretStorageDialog in a `BaseDialog`. The main thing this achieves
is a `FocusLock`.
* playwright: factor out helper for verification
We have two copies of the same code, and we're about to add a third...
* playwright: test for verifying from Settings
* Add a unit test for BaseDialog
