feat(bot-platform): migrate BotRegistry to Redis Streams consumer group

Replace pub/sub subscribe with XREADGROUP on bot game-start stream.
Remove dual-write from EventPublisher.publishGameStart.
Consumer group: bot-platform-consumer, XACK after forwarding.
Poll loop uses emitter identity to prevent thread leak on re-registration.
Group created with '$' offset — no historical replay on first connect.

Closes NCS-101
https://knockoutwhist.youtrack.cloud/issue/NCS-101

modules/account/src/main/scala/de/nowchess/account/service/EventPublisher.scala

@@ -36,7 +36,6 @@ class EventPublisher:
         new XAddArgs().maxlen(maxStreamLen).nearlyExactTrimming(),
         Map("data" -> json).asJava,
       )
-    redis.pubsub(classOf[String]).publish(s"${redisConfig.prefix}:bot:$botId:events", json)
     ()
 
   def publishChallengeCreated(destUserId: String, challengeId: String, challengerName: String): Unit =