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.

apps/bot/src/modules/verification/alt-detection.ts

@@ -0,0 +1,62 @@
+export type AltSignalMatch = {
+  reason: 'ip' | 'invite_cluster';
+  matchedUserId: string | null;
+};
+
+export type AltDetectionInput = {
+  userId: string;
+  accountAgeDays: number;
+  inviteCode: string | null;
+  ipHash: string | null;
+  /** Prior verification records in the same guild (excluding current user). */
+  priorRecords: Array<{
+    userId: string;
+    inviteCode: string | null;
+    ipHash: string | null;
+    createdAt: Date;
+    flaggedAsAlt: boolean;
+  }>;
+  altIpWindowDays: number;
+  altInviteWindowHours: number;
+  altMaxAccountsPerInvite: number;
+  /** Only flag invite clusters when the current account is this young or younger. */
+  youngAccountMaxDays?: number;
+};
+
+/**
+ * Detects likely alt accounts from Discord + captcha signals.
+ * Does not use browser fingerprinting beyond salted IP / UA hashes from the captcha page.
+ */
+export function detectAltAccount(input: AltDetectionInput): AltSignalMatch | null {
+  const youngMax = input.youngAccountMaxDays ?? 7;
+  const now = Date.now();
+
+  if (input.ipHash) {
+    const ipWindowMs = input.altIpWindowDays * 24 * 60 * 60 * 1000;
+    const ipMatch = input.priorRecords.find(
+      (record) =>
+        record.ipHash === input.ipHash &&
+        now - record.createdAt.getTime() <= ipWindowMs
+    );
+    if (ipMatch) {
+      return { reason: 'ip', matchedUserId: ipMatch.userId };
+    }
+  }
+
+  if (input.inviteCode && input.accountAgeDays <= youngMax) {
+    const inviteWindowMs = input.altInviteWindowHours * 60 * 60 * 1000;
+    const recentSameInvite = input.priorRecords.filter(
+      (record) =>
+        record.inviteCode === input.inviteCode &&
+        now - record.createdAt.getTime() <= inviteWindowMs
+    );
+    if (recentSameInvite.length >= input.altMaxAccountsPerInvite) {
+      return {
+        reason: 'invite_cluster',
+        matchedUserId: recentSameInvite[0]?.userId ?? null
+      };
+    }
+  }
+
+  return null;
+}