fix: drop player_id FK constraint — bots don't exist in profiles table

tournament_registrations.player_id had FK to profiles(id) which rejected
bot player inserts since bot UUIDs aren't real profiles. Dropped the
constraint so bot testing works.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

migrations/005_bot_tournament_testing.sql

 -- Migration 005: Bot Tournament Testing
 -- Adds is_bot flag to tournament_registrations for test player identification
 -- Adds swiss_round_id to el3ab_tournament_rounds for linking to Swiss API rounds
+-- Drops player_id FK to profiles (bots don't exist in profiles)
 
 ALTER TABLE tournament_registrations
     ADD COLUMN IF NOT EXISTS is_bot BOOLEAN DEFAULT FALSE,
@@ -9,5 +10,8 @@ ALTER TABLE tournament_registrations
 CREATE INDEX IF NOT EXISTS idx_tournament_registrations_bot
     ON tournament_registrations(tournament_id) WHERE is_bot = TRUE;
 
+ALTER TABLE tournament_registrations
+    DROP CONSTRAINT IF EXISTS tournament_registrations_player_id_fkey;
+
 ALTER TABLE el3ab_tournament_rounds
     ADD COLUMN IF NOT EXISTS swiss_round_id UUID;