Autofill usernames in the write-in section for elections

To prevent incorrect write-ins, it would be awesome if usernames were auto-filled like how they are in conditional's attendance tab.

Start by locating the write-in section and the conditional's attendance tab referenced in the issue, then compare how usernames are filled there. Implement equivalent username autofill for election write-ins, and verify that selecting or entering write-in candidates helps prevent incorrect usernames.

Written by the indexing model from the issue text.