- Wire next-themes ThemeProvider in layout with class strategy, defaultTheme=dark
- Define all Gemini colors as CSS custom properties (--gem-*) in globals.css
with light (:root) and dark (.dark) variants
- Replace all hardcoded hex colors across 7 Gemini components with var() refs
- Add Sun/Moon toggle button in GeminiTopbar (right side, before Settings)
- Theme persists to localStorage via next-themes (key: gem-theme)
- Dark theme renders identically to before (same hex values)
- Light theme: white bg, light gray surfaces, same blue-purple accent gradient
Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
