feat: add tournament creation wizard with participant management and bulk game entry

prisma/migrations/20260330200000_add_event_participant_unique/migration.sql

@@ -0,0 +1,2 @@
+-- Add unique constraint to EventParticipant table
+CREATE UNIQUE INDEX "event_participants_eventId_playerId_key" ON "event_participants"("eventId", "playerId");

prisma/schema.prisma

@@ -100,6 +100,7 @@ model EventParticipant {
   player           Player    @relation(fields: [playerId], references: [id])
   event            Event     @relation(fields: [eventId], references: [id])
 
+  @@unique([eventId, playerId])
   @@map("event_participants")
 }