Use reCAPTCHA v3 on password reset (#135)

## Summary
- Closes #134.
- Password reset loads reCAPTCHA v3 and sends `grecaptcha.execute(siteKey, { action: 'password_reset' })` as `recaptchaToken`.
- Removes `react-google-recaptcha`. That package is a v2 widget, and the Hesychia key is v3, so Google rejected the site key on https://hesychia.ai/password_reset/ before submit.
- Site key stays `6LfENu4qAAAAAFtPejcrP3dwBDxcRPjqi7RhytJJ`. The backend already checks the v3 token with `CAPTCHA_SECRET_KEY` and rejects a score under 0.5.

## Test plan
- [x] `CI=true npm test -- --watchAll=false --coverage=false --testPathPattern=pages/PasswordReset` (6 passed)
- [ ] After deploy, open https://hesychia.ai/password_reset/ and confirm the invalid reCAPTCHA error is gone
- [ ] Submit a real account email and confirm the reset email sends
- [ ] Submit again with a bad or blocked client and confirm the page shows "Unable to reset password"

Reviewed-on: #135

llm-fe/package-lock.json

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@@ -6540,15 +6538,6 @@
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@@ -19301,19 +19277,6 @@
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