1. pairings/results JSONB columns already decoded by Supabase — added
   is_array check before json_decode (same pattern as tiebreak fix).

2. Bot player_id was 'bot_xyz' string but column is UUID type — PostgREST
   silently rejected every insert. Now generates proper v4 UUIDs.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>