feat: monochrome black & white rebrand + new Pudu robots

- Convert site from royal-blue theme to black/white monochrome (desaturate
  all blue-hued colors; keep WhatsApp green and error red)
- Swap blue circular brand logo for mono YS mark; regenerate favicon/PWA icons
- Add 6 Pudu robots (CC1 Pro, MT1 Max, MT1 Vac, T600, T600 Underride, BG1 Pro)
- Fix favicon.ico to RGBA (Next 16 Turbopack decode) and Stripe apiVersion type

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/LanguageSwitcher.tsx

@@ -23,7 +23,7 @@ export function LanguageSwitcher() {
         backgroundColor: 'rgba(0, 0, 0, 0.04)',
         border: '1px solid rgba(0, 0, 0, 0.08)',
         borderRadius: '0.5rem',
-        color: '#0a0a0c',
+        color: '#0b0b0b',
         cursor: 'pointer',
         fontSize: '0.875rem',
         fontWeight: 500,