Reorganize the citizen page (/commune/[slug]) for voters: full-width
interactive chart with "Population" zoom by default, separate auth and
vote sections, countdown timer for vote deadline.
Backend: add vote_deadline column to communes with Alembic migration.
Admin: add deadline configuration card with datetime-local input.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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