* feat: add reset progress action for a candidate's quiz attempt
Admins previously had no way to let a candidate retake a quiz once
started. Adds a backoffice action that clears a candidate's given
answers and start timestamp for a quiz, closes#20.
* fix: wrap candidate progress reset in a transaction
Avoids leaving a candidate half-reset (answers deleted but started
still set) if the second flush fails. Addresses CodeRabbit review
comment on PR #204.
* feat: open candidate edit/add forms in modals with dirty-aware dismissal
Rename-candidate modal always blocked backdrop-click dismissal via a
hardcoded static backdrop; wire it into the existing bo--modal
controller so outside clicks/Escape only get blocked once the name
field has actually been edited. Also move "Add Candidate" from a
full-page navigation into the same turbo-frame modal pattern already
used for editing quiz questions, keeping the full-page form as a
fallback for non-JS/turbo requests.
* feat: show a hint for the candidates textarea and gate translations in CI
Add a help hint on the add-candidates form explaining one candidate per
line, and translate it plus a few strings from the earlier reset-progress
feature that had been missed. Also add a CI step that re-runs
translation:extract and fails the build if it produces uncommitted
changes, so untranslated/stale strings can't slip through review again.
* Just links
