feat: Passkey (WebAuthn) login (#1111)

* feat(auth): passkey (WebAuthn) login — server endpoints, schema + admin toggle

Add @simplewebauthn/server registration and primary (discoverable) login ceremonies under /api/auth/passkey, a webauthn_credentials + single-use webauthn_challenges schema (migration), the instance-wide passkey_login toggle (default off) enforced before auth by a guard, and require_mfa satisfaction via a verified passkey. RP ID/origin come only from server config (webauthn_rp_id/origins -> APP_URL), never request headers.

* feat(auth): passkey enrolment, login button + admin settings UI

PasskeysSection in account settings (add/rename/remove with a current-password step-up), a 'Sign in with a passkey' button on the login page, the admin enable + RP-ID/origins controls, and a per-user admin reset action.

* i18n(auth): passkey strings across all locales

Add login/settings/admin passkey keys to en and all 19 translated locales.

server/src/nest/auth/passkey-enabled.guard.ts

@@ -0,0 +1,22 @@
+import { CanActivate, HttpException, Injectable } from '@nestjs/common';
+import { resolveAuthToggles } from '../../services/authService';
+
+/**
+ * Server-side enforcement of the instance-wide `passkey_login` toggle. Placed
+ * BEFORE the auth guard on every passkey ceremony route so a disabled feature
+ * returns 404 (not "auth required") and cannot be driven by direct API calls —
+ * hiding the button in the UI is not enough. Mirrors JourneyAddonGuard.
+ *
+ * The credential-management routes (list/rename/delete) are deliberately NOT
+ * gated by this guard so users can still clean up their passkeys after an admin
+ * turns the feature off.
+ */
+@Injectable()
+export class PasskeyEnabledGuard implements CanActivate {
+  canActivate(): boolean {
+    if (!resolveAuthToggles().passkey_login) {
+      throw new HttpException({ error: 'Passkey login is not enabled' }, 404);
+    }
+    return true;
+  }
+}