1. Content-Type: application/json only sent when body is not null.
   Swiss API rejects bodiless POST/GET with that header.
2. Controller start() now calls Swiss API /start endpoint.
3. simulateNextRound() auto-starts Swiss tournament if local status
   is still draft/registration.
4. generateRound response parsing fixed — data is in {round:{id,...}}.
5. getPairings response wrapped in {data:[...]} — now handled.
6. Pairing field names use camelCase (whitePlayerId not white_player_id).
7. Player ratings fetched from listPlayers instead of expecting them
   embedded in pairing objects.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>