Clear race dialog when closed

[ArendPeter]

Currently when adding multiple races to an election the state of the dialog isn't fully reset

2025-01-13.17-13-26.mp4

Instead all fields should start at empty, and the voting method stepper should also reset to the first step

[ArendPeter]

@FarzeelAhmad99 Fixed the first half of this issue in #736 !

Still need one more piece though. In the voting method selector, the stepper is preserved when reopening the window, but this should reset to the first step

Farzeel, you should have received an invite to have triage permissions. Once you accept that I can assign this issue to you if you're interested