Improve the import dialog UX

> [!NOTE]
> As a user, I want to see the combatants I'm importing and inspect if everything is right.

There should be user feedback about how many combatants were parsed and how many failed.

The import dialog should display a list of combatants parsed and tell how many failed. Use https://pub.dev/packages/wolt_modal_sheet#basic-multi-page-example-app

Start by locating the import dialog and tracing how parsed and failed combatants are currently reported. Review the linked wolt_modal_sheet basic multi-page example for the dialog structure; done means the dialog lists parsed combatants and clearly reports both parsed and failed counts.

Written by the indexing model from the issue text.