Clear "already subscribed" newsletter error on next interaction

Matches standard form-validation behavior: any further edit to the
email or consent checkbox after the already-subscribed message
appears now dismisses it, instead of leaving it stuck until submit.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/challenge/components/EmailCapture.tsx

@@ -13,7 +13,7 @@ function LockIcon() {
 }
 
 export function EmailCapture({ buttonLabel = "Challenge starten" }: { buttonLabel?: string }) {
-  const { email, emailError, consent, setConsent, status, error, successMessage, emailRef, handleEmailChange, handleEmailBlur, handleSubmit } =
+  const { email, emailError, consent, handleConsentChange, status, error, successMessage, emailRef, handleEmailChange, handleEmailBlur, handleSubmit } =
     useNewsletterSignup("challenge");
 
   if (status === "success") {
@@ -60,7 +60,7 @@ export function EmailCapture({ buttonLabel = "Challenge starten" }: { buttonLabe
           type="checkbox"
           required
           checked={consent}
-          onChange={(e) => setConsent(e.target.checked)}
+          onChange={(e) => handleConsentChange(e.target.checked)}
           className="size-4 shrink-0 mt-0.5 rounded-xs border border-[#d9d9d9] accent-[#f6a701]"
         />
         <span className="text-[0.8rem] text-[#444] leading-normal">