Massive smoke columns

Added

• /smoke command — manage smoke columns from chat. Use /smoke list to see active campfires, /smoke reload to refresh them, or /smoke clear to remove them all
• Smoke columns now survive world reloads and server restarts — they reappear instantly when you log back in, no need to revisit the campfire
• Players who join late automatically see all active smoke columns

Fixed

• Fixed a crash when exiting the world