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

verification/verify_rate_limit.py

@@ -0,0 +1,60 @@
+from playwright.sync_api import sync_playwright, expect
+import time
+
+def verify_rate_limit():
+    with sync_playwright() as p:
+        browser = p.chromium.launch(headless=True)
+        page = browser.new_page()
+
+        print("Navigating to home...")
+        page.goto("http://localhost:3000")
+
+        print("Navigating to Contact...")
+        # Try both English and German just in case
+        try:
+            page.get_by_role("link", name="Contact").click()
+        except:
+            page.get_by_role("link", name="Kontakt").click()
+
+        # Fill form
+        print("Filling form...")
+        # Use placeholders from en.ts
+        page.get_by_placeholder("Your name").fill("Test User")
+        page.get_by_placeholder("your@email.com").fill("test@example.com")
+        page.get_by_placeholder("What is it about?").fill("Test Subject")
+        page.get_by_placeholder("Your message...").fill("Test Message")
+
+        # Submit 1
+        print("Submitting first time...")
+        submit_btn = page.get_by_role("button", name="Send Message")
+        submit_btn.click()
+
+        # Wait for result (likely error due to missing keys/network)
+        # We expect either success or error message
+        print("Waiting for response...")
+        # Allow some time for EmailJS timeout
+        try:
+            expect(page.get_by_text("Error sending message").or_(page.get_by_text("Message sent successfully"))).to_be_visible(timeout=10000)
+        except:
+            print("Timed out waiting for first response, checking if button is enabled...")
+
+        # Ensure button is enabled before clicking again
+        # If it's disabled, we can't click
+        expect(submit_btn).not_to_be_disabled()
+
+        # Submit 2
+        print("Submitting second time...")
+        submit_btn.click()
+
+        # Check for rate limit message
+        print("Checking for rate limit message...")
+        expect(page.get_by_text("Too many requests")).to_be_visible()
+
+        # Screenshot
+        print("Taking screenshot...")
+        page.screenshot(path="verification.png")
+
+        browser.close()
+
+if __name__ == "__main__":
+    verify_rate_limit()