Replaces the dark navy palette with a light grouped-background system:
- theme.ts: full token set (space/radius/type/shadow) + light+dark palettes
- ui.tsx: Screen/Title/SectionHeader/Card/Separator/Pill/Empty primitives
- TaskRow: rounded-square checkbox carrying priority colour, inset separators
- TaskListScreen: rows grouped into a card, drag lift, refined deferred footer
- Icon.tsx: dependency-free geometric icon set (emoji don't take a tint)
- home: large title, Next-up card, "needs attention" rows, icon tab bar
- Priority/Estimate/Date chips unified on the accent-soft active state
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
