Add a plain, utilitarian theme focused on readability and wayfinding:
- White/light gray land (#f5f5f5), soft pastel green parks (#c3ecb2)
- Gentle blue water (#aadaff) with classic road hierarchy
- White minor roads, yellow primary (#fbc02d), orange motorway (#f9a825)
- Pure white UI panels with Google-standard gray text
- All 73 protomaps flavor keys + pois + landcover objects
- Full UI CSS custom properties using Google color palette
- Overlay config for hillshade, contours, public lands, trails
Update theme switcher to cycle through all available themes.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
