ReFa Style Design System (DESIGN.md, Japanese UI)

Design policy: A refined beauty-tech brand. It pursues luxury, sophistication, and cleanliness to the fullest, building its worldview through product photography and typography. Rather than relying on decorative color, it generates expressiveness through the contrast of text size and letter spacing - Density: Editorial style with generous whitespace. The hero is a full-width slider, and sections have a spacious composition - Keywords: Premium, refined, clean, editorial, luxury - Characteristics: Rather than pure black (#000000), it adopts dark chocolate brown #231815 as the text color, produci