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

Design policy: Two poles of white and black + a single point of orange. Explain in white sections, assert in black sections. Color is used to guide only the CTA. - About UPSIDER: A corporate card for the administrative departments / CFOs of public companies and startups. The appeal axes are "credit limits up to 1 billion yen," "speed of response," and "virtually zero fraudulent use," with a composition that shows numbers large throughout. - Density: Low. h1 is 64px, h2 is 48px, and the vertical padding of black sections is 160px. One message per screen. - Keywords: orange gradient pill, two-tr