Enhance verification system with multi-provider support and alt-account detection

- Added support for multiple captcha providers including Google reCAPTCHA (v2 and v3), hCaptcha, and Cloudflare Turnstile.
- Introduced new fields in the verification configuration for selecting captcha providers and enabling alt-account detection.
- Implemented logic to handle verification attempts and flag potential alt accounts based on IP and invite code analysis.
- Updated environment configuration to include necessary keys for captcha providers.
- Enhanced the user interface to allow selection of captcha providers in the verification setup.
- Improved backend handling of verification records to store additional data related to captcha provider usage.

.env.example

@@ -39,3 +39,24 @@ LEGAL_OPERATOR_NAME=HexaHost Inh. Samuel Müller
 LEGAL_OPERATOR_ADDRESS=Richard-Miller-Straße 1, 94051 Hauzenberg, Deutschland
 LEGAL_OPERATOR_EMAIL=info@hexahost.de
 LEGAL_OPERATOR_PHONE=+49 15566 175855
+
+# ---------------------------------------------------------------------------
+# Verification captcha providers (WebUI). Leave empty to disable a provider.
+# MATH always works without keys. Per-guild provider is chosen in the dashboard.
+# ---------------------------------------------------------------------------
+# Google reCAPTCHA v2 (checkbox) – https://www.google.com/recaptcha/admin
+RECAPTCHA_SITE_KEY=
+RECAPTCHA_SECRET_KEY=
+# Google reCAPTCHA v3 (score-based). Falls back to RECAPTCHA_* if unset.
+RECAPTCHA_V3_SITE_KEY=
+RECAPTCHA_V3_SECRET_KEY=
+RECAPTCHA_V3_MIN_SCORE=0.5
+# hCaptcha – https://dashboard.hcaptcha.com
+HCAPTCHA_SITE_KEY=
+HCAPTCHA_SECRET_KEY=
+# Cloudflare Turnstile – https://dash.cloudflare.com → Turnstile
+TURNSTILE_SITE_KEY=
+TURNSTILE_SECRET_KEY=
+# Salt for hashing client IPs used in alt-account detection (min 16 chars).
+# Generate e.g. with: openssl rand -hex 16
+CAPTCHA_IP_HASH_SALT=