revert(account): restore original two-persist pattern for OfficialBotAccount token

Reverts the Hibernate-related changes introduced during PR review:
- Remove nullable = false from OfficialBotAccount.token (caused PropertyValueException
  at first persist() since token is assigned after id is generated)
- Restore double persist() pattern: first persist() gets generated UUID, then token
  is generated using that id and entity is persisted again with dirty tracking

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

modules/account/src/main/scala/de/nowchess/account/domain/UserAccount.scala

@@ -76,6 +76,6 @@ class OfficialBotAccount extends PanacheEntityBase:
 
   var createdAt: Instant = uninitialized
 
-  @Column(nullable = false, length = 1024)
+  @Column(length = 1024)
   var token: String = uninitialized
   // scalafix:on

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

@@ -205,7 +205,8 @@ class AccountService:
     bot.name = botName
     bot.createdAt = Instant.now()
     officialBotAccountRepository.persist(bot)
-    bot.token = generateBotToken(bot.id, botName)
+    bot.token = generateBotToken(bot.id, bot.name)
+    officialBotAccountRepository.persist(bot)
     Right(bot)
 
   @Transactional
@@ -216,7 +217,8 @@ class AccountService:
         bot.name = name
         bot.createdAt = Instant.now()
         officialBotAccountRepository.persist(bot)
-        bot.token = generateBotToken(bot.id, name)
+        bot.token = generateBotToken(bot.id, bot.name)
+        officialBotAccountRepository.persist(bot)
         log.infof("Auto-registered official bot: %s", name)
     }