Cloudflare Turnstile en login y registro (Next.js)

- lib/turnstile.ts: verifyTurnstile(token, ip) contra siteverify (fail-closed).
- components/Turnstile.tsx: widget cliente (carga el script de Cloudflare, callback
  con el token). Site key por NEXT_PUBLIC_TURNSTILE_SITE_KEY; secreto server-only.
- LoginForm/RegisterForm: widget + token en el POST; submit deshabilitado hasta
  resolver el captcha (si hay site key).
- Routes login/register: verifican el token antes de continuar (error captchaFailed).
- Catálogos: captchaFailed.

Verificado: POST sin token -> captchaFailed en login y registro (enforcement server).

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

web-next/app/[locale]/login/LoginForm.tsx

@@ -3,8 +3,10 @@
 import { useState } from 'react'
 import { useTranslations } from 'next-intl'
 import { useRouter } from '@/i18n/navigation'
+import { Turnstile } from '@/components/Turnstile'
 
-const ERROR_KEYS = ['invalidCredentials', 'missingFields', 'invalidRequest'] as const
+const ERROR_KEYS = ['invalidCredentials', 'missingFields', 'invalidRequest', 'captchaFailed'] as const
+const SITE_KEY = process.env.NEXT_PUBLIC_TURNSTILE_SITE_KEY
 
 export function LoginForm() {
   const t = useTranslations('Login')
@@ -13,6 +15,7 @@ export function LoginForm() {
   const [password, setPassword] = useState('')
   const [showPw, setShowPw] = useState(false)
   const [busy, setBusy] = useState(false)
+  const [captcha, setCaptcha] = useState('')
   const [message, setMessage] = useState<{ ok: boolean; text: string } | null>(null)
 
   async function handleSubmit(e: React.FormEvent) {
@@ -29,7 +32,7 @@ export function LoginForm() {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         credentials: 'same-origin',
-        body: JSON.stringify({ email: email.trim(), password }),
+        body: JSON.stringify({ email: email.trim(), password, turnstileToken: captcha }),
       })
       const data: { success?: boolean; needsSelection?: boolean; error?: string } = await res.json()
       if (data.success) {
@@ -77,9 +80,10 @@ export function LoginForm() {
             {showPw ? '🙈' : '👁'}
           </button>
         </div>
+        <Turnstile onVerify={setCaptcha} />
         <button
           type="submit"
-          disabled={busy}
+          disabled={busy || (!!SITE_KEY && !captcha)}
           className="w-full rounded bg-amber-600 px-4 py-2 font-semibold text-[#1b120b] disabled:opacity-60"
         >
           {busy ? t('connecting') : t('submit')}