feat: transform UI to dark cyberpunk theme

- Eliminate all white/light boxes and backgrounds
- Fix drag-drop zone with neon cyberpunk colors (#00f0ff, #ff006e, #16213e)
- Fix restored mnemonic display with matrix green (#39ff14)
- Fix security options panel with dark gradient
- Fix all remaining slate-700/slate-800 labels to cyberpunk neon
- Fix info banners and text colors
- Update badge components with cyberpunk color scheme
- Apply consistent dark theme across all components

src/components/Footer.tsx

@@ -8,7 +8,7 @@ interface FooterProps {
 
 const Footer: React.FC<FooterProps> = ({ appVersion, buildHash, buildTimestamp }) => {
     return (
-        <footer className="text-center text-xs text-slate-400 p-4">
+        <footer className="text-center text-xs text-[#6ef3f7] p-4">
             <p>SeedPGP v{appVersion} • build {buildHash} • {buildTimestamp}</p>
             <p className="mt-1">Never share your private keys or seed phrases. Always verify on an airgapped device.</p>
         </footer>