feat(captcha): add provider-based captcha support (Google v3 + Cloudflare Turnstile)

[NullSablex]

• Add centralized captcha settings/validation methods in erLhcoreClassUserValidator:
  getCaptchaSettings, validateAuthCaptcha, verifyGoogleRecaptchaV3,
  verifyCloudflareTurnstile, and postCaptchaVerifyRequest.
• Replace inline captcha verification in modules/lhuser/login.php and
  modules/lhuser/forgotpassword.php with shared validation.
• Update auth captcha error handling to use the generic string
  Captcha validation failed.
• Extend system/recaptcha admin handling with provider support (google/turnstile),
  new Turnstile fields, and CSRF redirect fix to system/recaptcha.
• Update captcha admin template with provider selector and provider-specific sections;
  use shared key labels (Site key / Secret key) in both provider blocks.
• Update shared captcha rendering template to support:
  Google v3 token flow and Cloudflare Turnstile widget flow.
• Set explicit captcha actions in auth templates:
  login_action and forgot_password_action.
• Update install defaults (modules/lhinstall/install.php, cli/lib/install.php)
  to include provider and Turnstile keys in recaptcha_data.
• Update translation catalogs (doc/translation_default/translation_web.ts,
  translations/*/translation.ts, including translations/en_EN/translation.ts)
  with the new captcha-related keys used by these changes.

[NullSablex]

Peço desculpas caso haja erros; esta é a minha primeira contribuição pública em algum projeto.

I apologize in case there are any mistakes; this is my first public contribution to a project.

[remdex]

Hi,

Thanks for effort, I'll try to review during this/next week :)