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

Design policy: Build hierarchy with white and gray alone. Rather than guiding users with a brand color, the design decides "where to look" using only the near-black filled button #1a1a1a, the pale surface #eff1f4, and the amount of whitespace. Unusually for a SaaS service site, saturation is completely zero. - About hacomono: A business system that handles enrollment, booking, payment, and membership management for stores, facilities, and schools entirely online. Because it targets a wide range of customers — gyms, schools, public facilities — it is designed so that the UI itself carries no in