feat: add client-side rate limiting to contact form

- Added `useRateLimit` hook
- Integrated hook into `Contact.tsx`
- Added translations for rate limit error
- Added unit tests
- Fixed type error in `Button.tsx` to allow build to pass

src/i18n/en.ts

@@ -98,6 +98,7 @@ export const en: Translations = {
       sending: 'Sending...',
       success: 'Message sent successfully! I\'ll get back to you soon.',
       error: 'Error sending message. Please try again or contact me directly.',
+      rateLimit: 'Too many requests. Please wait a moment.',
     },
     info: {
       title: 'Contact Info',