Implement persistent hardcore death bans (XUID + IP) for dedicated server

On the dedicated server, hardcore death now persists XUID and IP bans to
banned-players.json and banned-ips.json via the Access system, and
disconnects the player. Bans survive server restarts. Client-hosted games
retain the existing in-memory XUID ban with force-save behavior.

- Add hardcore property to server.properties (forces Hard difficulty)
- Add LevelData::setHardcore() so loaded worlds respect the server config
- Add PlayerList::banPlayerForHardcoreDeath() with persistent XUID + IP bans
- Reject respawn requests server-side in hardcore mode
- Ensure server-side player ticks run without move packets (fixes
  environmental damage not applying for some clients)
- Restore 0x8 hardcore bit on LoginPacket/RespawnPacket wire format so
  the client-side death screen detects hardcore mode correctly

Minecraft.Client/ServerPlayer.cpp

@@ -574,10 +574,10 @@ void ServerPlayer::die(DamageSource *source)
 	{
 		setGameMode(GameType::ADVENTURE);
 
-		// Ban this player's XUID and force-save so the host
-		// cannot circumvent the death by quitting without saving.
-		server->getPlayers()->banXuid(getOnlineXuid());
-		app.SetXuiServerAction(ProfileManager.GetPrimaryPad(), eXuiServerAction_SaveGame);
+		// Ban this player's XUID and queue disconnect.
+		// The force-save is triggered inside banPlayerForHardcoreDeath after the
+		// disconnect is queued, so the client doesn't get stuck on a save screen.
+		server->getPlayers()->banPlayerForHardcoreDeath(this);
 	}
 
 	if (!level->getGameRules()->getBoolean(GameRules::RULE_KEEPINVENTORY))