refactor: replace hardcoded hex colors with theme tokens, move data/ to root

- Add --color-green-mid token (#4a7a55) to @theme for dimmer stat values
- Replace all text-[#hex]/bg-[#hex] arbitrary values with named tokens:
  text-green, text-green-light, text-green-sec, text-green-muted,
  text-green-dark, text-green-mid, text-text, bg-card, bg-bg, border-border
- Replace rgba(34,197,94,X) inline styles with bg-green/X opacity modifiers
- Convert single-prop style={{ borderColor/background }} to className
- Fix SVG stroke="#dff5e8" → stroke="currentColor"
- Use CSS variables in globals.css base styles (background-color, color)
- Move app/data/wikipedia/ → data/ (project root, not inside Next.js app dir)
- Update Dockerfile, seed.ts, scrape-wikipedia.ts paths accordingly
- Remove unused app/data/world_cup.csv

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/layout.tsx

@@ -35,11 +35,11 @@ export default function RootLayout({ children }: { children: React.ReactNode })
         <AppApolloProvider>
           <Nav />
           <main className="pt-[60px] min-h-screen">{children}</main>
-          <footer className="border-t mt-8" style={{ borderColor: 'rgba(34,197,94,0.08)' }}>
-            <div className="max-w-[1200px] mx-auto px-7 py-6 flex flex-col sm:flex-row items-center justify-between gap-2 text-[11px] text-[#1a3a22]">
+          <footer className="border-t border-green/8 mt-8">
+            <div className="max-w-[1200px] mx-auto px-7 py-6 flex flex-col sm:flex-row items-center justify-between gap-2 text-[11px] text-green-dark">
               <span>© {new Date().getFullYear()} World Cup Statistics.</span>
               <a href="https://dev.pivoine.art" target="_blank" rel="noopener noreferrer"
-                className="text-[#2a5c35] hover:text-[#22c55e] transition-colors">
+                className="text-green-muted hover:text-green transition-colors">
                 dev.pivoine.art
               </a>
             </div>