fix(account): fix EntityExistsException in syncOfficialBots/createOfficialBotAccount

Pre-assigning bot.id on a @GeneratedValue entity causes Hibernate 6 to treat
it as detached, throwing PersistentObjectException on persist(). Fix: persist
with null id (Hibernate assigns UUID immediately in-memory), then set token on
the now-managed entity — dirty tracking commits the token at transaction flush.
No second persist() call needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -201,26 +201,22 @@ class AccountService:
 
   @Transactional
   def createOfficialBotAccount(botName: String): Either[AccountError, OfficialBotAccount] =
-    val id  = UUID.randomUUID()
     val bot = new OfficialBotAccount()
-    bot.id = id
     bot.name = botName
     bot.createdAt = Instant.now()
-    bot.token = generateBotToken(id, botName)
     officialBotAccountRepository.persist(bot)
+    bot.token = generateBotToken(bot.id, botName)
     Right(bot)
 
   @Transactional
   def syncOfficialBots(botNames: List[String]): Unit =
     botNames.foreach { name =>
       if officialBotAccountRepository.findByName(name).isEmpty then
-        val id  = UUID.randomUUID()
         val bot = new OfficialBotAccount()
-        bot.id = id
         bot.name = name
         bot.createdAt = Instant.now()
-        bot.token = generateBotToken(id, name)
         officialBotAccountRepository.persist(bot)
+        bot.token = generateBotToken(bot.id, name)
         log.infof("Auto-registered official bot: %s", name)
     }