Moves the four bounds-checked remove-by-index handlers
(--remove-creature, --remove-object, --remove-quest,
--remove-item) out of main.cpp into a new
cli_remove.{hpp,cpp} module. All four share the same
load-erase-save pattern with index validation and a "what
was removed" report for audit trails. The first three use
their respective editor classes (NpcSpawner, ObjectPlacer,
QuestEditor); --remove-item walks raw nlohmann::json since
items.json doesn't have a dedicated editor class yet.
main.cpp shrinks by 145 lines (6,131 to 5,986).
