Add ThemeContext (dark/light, persisted to localStorage, applied as
data-theme on <html>). Theme toggle is a sun/moon flip switch at the
right end of the dashboard info bar.
CSS overrides in index.css target every hardcoded Tailwind arbitrary
colour class used across all pages via [data-theme="light"] selectors,
so the entire panel switches without touching individual page files.
Light palette: page #f0f4f8, cards/sidebar #ffffff, hover #f1f5f9,
borders #e2e8f0, text #0f172a. Chart tooltip is made theme-aware via
inline-style interpolation since Tailwind CSS overrides cannot reach
Recharts inline styles.
NixReaper
ddb51a8b4d