Cambio de email con doble confirmación (completa el bloque de auth)

- lib/change-email.ts: requestEmailChange (valida pass/email/token, crea activación
  con old_email/old_email_hash, email al correo actual), confirmOldEmail (marca is_used,
  email al nuevo), confirmNewEmail (re-deriva verifier con el nuevo email + actualiza
  battlenet_accounts y account; borra la activación).
- components/ConfirmClient.tsx: cliente genérico que confirma un hash por POST al abrir.
- Routes /api/account/change-email, /confirm-old-email, /confirm-new-email.
- Páginas /change-email (protegida) y /confirm-old-email, /confirm-new-email (auto).
- Catálogos ChangeEmail, ConfirmOldEmail, ConfirmNewEmail.

Verificado: change-email protegida (401/redirect), confirmaciones con hash inválido
-> invalidLink sin crash. AUTH 100% reimplementado en Next.js.

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

web-next/messages/en.json

@@ -206,5 +206,36 @@
     "wrongCurrentPassword": "The current password is incorrect.",
     "accountNotFound": "Account not found.",
     "genericError": "Something went wrong. Please try again later."
+  },
+  "ChangeEmail": {
+    "title": "Change email",
+    "info": "The current email must be entered exactly, respecting case. The new email must be a Gmail address. You need a security token.",
+    "currentPassword": "Current password",
+    "currentEmail": "Current email",
+    "newEmail": "New email",
+    "confEmail": "Confirm new email",
+    "token": "Security token",
+    "submit": "Change email",
+    "sending": "Sending…",
+    "success": "A confirmation email has been sent to your current email.",
+    "missingFields": "Please fill in all fields.",
+    "wrongCurrentEmail": "The current email is not correct.",
+    "invalidEmail": "The new email is not valid.",
+    "invalidToken": "The security token is incorrect.",
+    "wrongCurrentPassword": "The current password is incorrect.",
+    "genericError": "Something went wrong. Please try again later."
+  },
+  "ConfirmOldEmail": {
+    "title": "Confirm email change",
+    "activating": "Confirming…",
+    "success": "Current email confirmed. Check your NEW email to complete the second step.",
+    "error": "The link is invalid or has already been used."
+  },
+  "ConfirmNewEmail": {
+    "title": "Confirm new email",
+    "activating": "Applying the change…",
+    "success": "Email changed successfully! You can now sign in with the new email.",
+    "error": "The link is invalid, expired or the account was not found.",
+    "goLogin": "Go to sign in"
   }
 }