Add a setting to turn off follow-up questions

The optional "FOLLOW-UP QUESTIONS" reinforcement section shown during
answer review is now gated behind a Settings toggle (on by default),
persisted locally the same way as dark mode and interface sounds.

scripts/ui/question_player.gd

@@ -1811,6 +1811,9 @@ func _render_review_followups() -> void:
 	if review_followups_content == null:
 		return
 	_clear_container_children(review_followups_content)
+	if not BlockSessionService.show_review_followups:
+		review_followups_section.visible = false
+		return
 	var question := BlockSessionService.get_current_question()
 	var authored: Array = question.get("review_followups", [])
 	if review_followup_states.size() != authored.size():