feat(security): alert on a new-device sign-in

On a completed sign-in (password, second-factor, or passkey) from a device or
location not seen before, send one notification through the dispatcher cascade,
honouring the user's per-channel preferences via a new SECURITY_ALERT event
type. Dedupe on a one-way, per-user fingerprint: a SHA-256 over the userId, the
coarse User-Agent family, and a country/ASN-level geo signal, stored in the new
user_known_devices ledger (migration 0203). The first sighting of a fingerprint
alerts and records; later sightings only bump last-seen and stay silent. The
raw User-Agent and IP are never persisted — only the salted hash and a coarse
label. Registration records its device silently so a fresh account does not
alert on its own first session. The whole path is fire-and-forget and never
blocks or fails a sign-in.

src/app/api/auth/passkey/login-verify/route.ts

@@ -1,5 +1,6 @@
 import { verifyAuthentication } from "@/lib/auth/passkey";
 import { createSession } from "@/lib/auth/session";
+import { recordSignInDevice } from "@/lib/auth/login-alert";
 import { auditLog } from "@/lib/auth/audit";
 import { apiSuccess, apiError, safeJson } from "@/lib/api-response";
 import { prisma } from "@/lib/db";
@@ -76,6 +77,9 @@ export const POST = apiHandler(async (request: NextRequest) => {
     ipAddress: ip,
   });
 
+  // v1.23 — new-device / new-location alert, fire-and-forget (see finishLogin).
+  void recordSignInDevice({ userId: user.id, ip, userAgent: ua });
+
   annotate({ action: { name: "auth.login.passkey" } });
 
   if (

src/app/api/auth/register/route.ts

@@ -6,6 +6,7 @@ import {
 import { registerSchema } from "@/lib/validations/auth";
 import { hashPassword, checkPasswordStrength } from "@/lib/auth/password";
 import { createSession } from "@/lib/auth/session";
+import { recordSignInDevice } from "@/lib/auth/login-alert";
 import { auditLog } from "@/lib/auth/audit";
 import {
   apiSuccess,
@@ -19,6 +20,8 @@ import { NextRequest, NextResponse } from "next/server";
 import { apiHandler } from "@/lib/api-handler";
 import { annotate } from "@/lib/logging/context";
 import { resolveServerLocale } from "@/lib/i18n/server-locale";
+import { checkPasswordBreach } from "@/lib/auth/hibp";
+import { getServerTranslator } from "@/lib/i18n/server-translator";
 import {
   isValidTimezone,
   resolveServerDefaultTimezone,
@@ -121,6 +124,17 @@ export const POST = apiHandler(async (request: NextRequest) => {
       422,
     );
   }
+
+  // v1.23 — reject a registration password found in a known breach corpus
+  // (HIBP k-anonymity). Fail-open on an unreachable HIBP.
+  const breach = await checkPasswordBreach(password);
+  if (breach?.breached) {
+    return apiError(
+      getServerTranslator(locale).t("auth.passwordBreached"),
+      422,
+    );
+  }
+
   const passwordHash = await hashPassword(password);
 
   // v1.15.20 — consume the invite LAST, after every other validation,
@@ -176,6 +190,16 @@ export const POST = apiHandler(async (request: NextRequest) => {
   const ua = request.headers.get("user-agent");
   await createSession(user.id, true, ip, ua);
 
+  // v1.23 — record the registering device silently so the account's first
+  // login from this same device does not immediately fire a "new device"
+  // alert. A genuinely new device later still alerts on its first sighting.
+  void recordSignInDevice({
+    userId: user.id,
+    ip,
+    userAgent: ua,
+    alertOnNew: false,
+  });
+
   // Stamp the consumer onto the invite (informational, best-effort —
   // the use itself was already counted atomically above).
   if (inviteId) {