Feature request: Check for already sent deposits on deposit page.

Problem: If the deposit process for multiple validators is aborted and then started again by uploading the json file again the launchpad will send the eht again.

Maybe it could check which deposits are already made and not offer those transactions.

The issue names no files, tests, or entry points. Trace the deposit page flow and determine how previously submitted validator deposits can be identified after re-uploading the JSON; done means already-made deposits are not offered again and duplicate transactions are not sent.

Written by the indexing model from the issue text.