light theme toggle implementation

[dima648228]

What & why

Implemented light/dark theme toggle feature

How

Added a persisted theme slice (light | dark) to the Zustand store in src/state/store.ts.

Dynamic Styling: updated tailwind.config.ts to use CSS variables for the ink palette. This allows the ui to swap colors automatically when the .dark class is toggled on the root element, while preserving support for tailwind's opacity modifiers

User Interface:

• Added a theme toggle button in TopBar.tsx.
• Updated HelpModal.tsx to document the new shortcut.
• Map Integration: Synchronized the MapLibre basemap with the application theme. Switching to light mode now swaps the CartoDB source to light_all.

Checklist

• pnpm typecheck clean
• pnpm test passing
• pnpm build succeeds
• If a lib was changed, unit tests are added or updated
• If a UI feature was added, the README feature table is updated

Screenshots / GIFs

Result

Light mode:

Dark mode