GET /rounds/current returns the active round's id/status, opened_at/
closes_at (derived from ROUND_DURATION_SECONDS), participant count and
jackpot (participant_count * bet_amount_sats). No active round still
returns bet_amount_sats so clients can render a fixed-entry hint either
way.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
