2段階認証（2FA）の設定

<h2>Two-Factor Authentication</h2>

<p>Keep your account safe by adding a second verification step when you sign in.</p>

<h3>How to enable 2FA</h3>

<ol>
  <li>Go to <strong>Profile Settings</strong> &gt; <strong>Account</strong> &gt; <strong>Security</strong>.</li>
  <li>Tap <strong>Enable Two-Factor Authentication</strong>.</li>
  <li>Choose your method:
    <ul>
      <li><strong>Authenticator app</strong> (recommended) — Scan the QR code with an app like Google Authenticator, Authy, or 1Password.</li>
      <li><strong>SMS</strong> — Receive a verification code by text message.</li>
    </ul>
  </li>
  <li>Enter the verification code to confirm setup.</li>
  <li>Save the backup codes provided. These let you sign in if you lose access to your 2FA method.</li>
</ol>

<h3>Signing in with 2FA</h3>

<p>After entering your email and password, you'll be asked for a verification code. Open your authenticator app or check your text messages, enter the 6-digit code, and you're in.</p>

<h3>Lost access to your 2FA method?</h3>

<p>Use one of the backup codes you saved during setup. Each code can be used once. If you've used all your backup codes, contact <a href="mailto:[email protected]">[email protected]</a> to regain access — you'll need to verify your identity.</p>