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/PlayerList.h

@@ -137,6 +137,7 @@ public:
 	void queueSmallIdForRecycle(BYTE smallId);
 	bool isXuidBanned(PlayerUID xuid);
 	void banXuid(PlayerUID xuid);  // 4J Added - for hardcore mode ban-on-death
+	void banPlayerForHardcoreDeath(ServerPlayer *player);  // Persistent XUID + IP ban on hardcore death
 	// AP added for Vita so the range can be increased once the level starts
 	void setViewDistance(int newViewDistance);
 };