- Prevent payment item from being consumed when submitting unchanged powers
- Reorder ServerPlayer::openBeacon to send ContainerOpenPacket before
addSlotListener so beacon data packets arrive after the client menu is ready
- Add BeaconMenu::broadcastChanges() to continuously sync levels and powers
to clients, matching the pattern FurnaceMenu already uses
- Initialize UIControl_BeaconEffectButton::m_lastState to prevent stale
heap memory from suppressing Iggy ChangeState calls on menu re-entry
1. Improve const correctness in a few places (such as `Container::getMaxStackSize()` -> `Container::getMaxStackSize() const`)
2. Use C++11 varargs for `I18n::get`, `Entity::newDoubleList` and `Language::getElement`