feat: add passkey management and auth policy sections to tenant settings

Adds PasskeySection (list/rename/delete passkeys), AuthPolicySection
(MFA mode + passkey enable/mode controls), and PasskeyNudgeBanner
(dismissable nudge for users without a passkey enrolled).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/sign-in/package.json

@@ -10,6 +10,7 @@
   },
   "dependencies": {
     "@cameleer/design-system": "^0.1.54",
+    "@simplewebauthn/browser": "^13.3.0",
     "react": "^19.0.0",
     "react-dom": "^19.0.0"
   },