Dark Mode DARK/LIGHT MODE: - 3-way picker (system/light/dark) is the standard pattern: @AppStorage("appearance") private var appearance: String = "system" private var preferredColorScheme: ColorScheme? { switch appearance { case "light": return .light; case "dark": return .dark; default: return nil } } .preferredColorScheme(preferredColorScheme) // on outermost container in @main app - CRITICAL: .preferredColorScheme() MUST be in the root @main app, NOT just in the settings view. - System option: .preferredColorScheme(nil) follows device setting. - Settings screen: Picker with light/dark/syst…