Integrate O3 with the Authentication module

The OpenMRS Authentication module supports powerful features like Multi-Factor Authentication and TOTP, but there is no working integration with the modern O3 frontend. When the backend issues a secondary authentication challenge, O3 has no way to handle it gracefully and will breaking the user's workflow and losing their unsaved work. My plan is to fix this on both sides. On the backend, I will update the backend to return structured JSON responses instead of legacy redirects, and expose new REST endpoints for TOTP setup and verification. On the frontend, I will update to pause and replay requests around authentication challenges, and build the React components that handle the TOTP flow that all without interrupting what the user was doing.