1. ApiProxy was sending Content-Type: application/json on GET requests
   which the Swiss API rejects ("Body cannot be empty when content-type
   is set to application/json"). Now only sends Content-Type for
   POST/PATCH/PUT methods.

2. Players tab now reads bot name/rating from bot_metadata JSONB
   instead of non-existent player_name/rating columns.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>