Feature-gate Dynamic Questions and CCS Cases to UAT only

Both are still in progress and shouldn't be reachable in production
(or local dev) yet - hide every entry point (nav sidebar, the
dashboard's "dynamic concepts due" review card, and the CCS Cases
mode card on the study selector) unless step3/deployment_environment
is "uat", the same setting that already drives the UAT badge. Added
Brand.is_uat_environment() as the shared check.

scripts/ui/medmind_style.gd

@@ -26,6 +26,10 @@ static func ranaze_mark_texture() -> Texture2D:
 	return preload("res://assets/branding/ranaze-mark.png")
 
 
+static func is_uat_environment() -> bool:
+	return str(ProjectSettings.get_setting("step3/deployment_environment", "development")) == "uat"
+
+
 static func text_color(dark: bool) -> Color:
 	return DARK_TEXT if dark else LIGHT_TEXT