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

Design philosophy: A calm media platform that prioritizes readability above all. It values the experience of both writers and readers, with content as the star of the design - Density: Generous whitespace. The article content area is 620px wide, emphasizing readability - Keywords: Easy to read, warm, minimal, content-first, calm - Characteristics: Rather than pure black (#000000), it uses near-black #08131a to provide a softer reading experience. Full dark mode support