Tailwind CSS v4, configured entirely through src/app/globals.css's
@theme inline block — there's no tailwind.config.ts, which v4
doesn't require for a project this size. Custom tokens
(--color-surface, --color-violet, --gradient-sunset, etc.) are
defined once in :root and mapped into Tailwind's theme so they're
usable as ordinary utility classes (bg-surface, text-violet,
bg-gradient-sunset).
Two font families: Space Grotesk (font-heading) for display text,
Inter (default font-sans) for body copy — both loaded via
next/font/google in src/app/layout.tsx.