fix: enable official bots to connect to external tournament server

Two bugs prevented official bots from joining the external tournament-server:

1. JWT claim mismatch — bot tokens lacked the `isBot: true` claim the
   tournament server requires. Added the claim to generateBotToken() in
   AccountService, which covers both user-owned bots and official bots.

2. Broken join flow — TournamentBotGamePlayer.joinTournament() called
   registerBot() which hit POST /api/auth/register on the tournament server,
   an endpoint that does not exist. Removed registerBot() and updated
   JoinTournamentRequest to accept a botToken field so the caller supplies
   the pre-existing NowChessSystems token directly.

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

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

@@ -239,6 +239,7 @@ class AccountService:
       .subject(botId.toString)
       .expiresAt(Long.MaxValue)
       .claim("type", "bot")
+      .claim("isBot", true)
       .claim("name", botName)
       .sign()
 

modules/official-bots/src/main/scala/de/nowchess/bot/resource/JoinTournamentRequest.scala

@@ -2,6 +2,7 @@ package de.nowchess.bot.resource
 
 case class JoinTournamentRequest(
     tournamentId: String,
+    botToken: String,
     difficulty: String,
     serverUrl: Option[String],
 )

modules/official-bots/src/main/scala/de/nowchess/bot/resource/TournamentJoinResource.scala

@@ -33,7 +33,7 @@ class TournamentJoinResource:
       difficulty,
       serverUrl,
     )
-    player.joinTournament(req.tournamentId, difficulty, serverUrl) match
+    player.joinTournament(req.tournamentId, req.botToken, difficulty, serverUrl) match
       case Right(botId) =>
         val resp = JoinTournamentResponse(botId, difficulty, "joining")
         Response.ok(resp).build()

modules/official-bots/src/main/scala/de/nowchess/bot/service/TournamentBotGamePlayer.scala

@@ -50,11 +50,11 @@ class TournamentBotGamePlayer:
         log.infof("Tournament bot enabled — server=%s tournament=%s bot=%s", cfg.serverUrl, cfg.tournamentId, cfg.botId)
         startAsync(cfg)
 
-  def joinTournament(tournamentId: String, difficulty: String, serverUrl: String): Either[String, String] =
-    registerBot(serverUrl, difficulty) match
-      case None => Left("Failed to register bot with tournament server")
-      case Some((botId, token)) =>
-        val cfg = TournamentBotConfig(serverUrl, tournamentId, token, botId, difficulty)
+  def joinTournament(tournamentId: String, botToken: String, difficulty: String, serverUrl: String): Either[String, String] =
+    TournamentBotConfig.jwtSubject(botToken) match
+      case None => Left("Invalid bot token — could not extract subject")
+      case Some(botId) =>
+        val cfg = TournamentBotConfig(serverUrl, tournamentId, botToken, botId, difficulty)
         if join(cfg) then
           startAsync(cfg)
           Right(botId)
@@ -65,26 +65,6 @@ class TournamentBotGamePlayer:
     thread.setDaemon(true)
     thread.start()
 
-  private def registerBot(serverUrl: String, difficulty: String): Option[(String, String)] =
-    Try {
-      val name = s"NowChess ${difficulty.capitalize}"
-      val body = s"""{"name":"$name","isBot":true}"""
-      val response = client
-        .target(serverUrl)
-        .path("api")
-        .path("auth")
-        .path("register")
-        .request(MediaType.APPLICATION_JSON)
-        .post(Entity.entity(body, MediaType.APPLICATION_JSON))
-      if response.getStatus == 201 then
-        val node  = objectMapper.readTree(response.readEntity(classOf[String]))
-        val id    = node.path("id").asText()
-        val token = node.path("token").asText()
-        response.close()
-        if id.nonEmpty && token.nonEmpty then Some((id, token)) else None
-      else { log.warnf("Bot registration returned status %d", response.getStatus); response.close(); None }
-    }.getOrElse(None)
-
   @PreDestroy
   def cleanup(): Unit =
     running = false