- Fastify backend with auth (CryptoPro CAdES-BES), KM check, UPD parsing - React frontend with auth page, code check, XML upload, results table - Client-side signing via crypto-pro 2.3.0 (browser plugin) - Token caching with auto-refresh, retry with exponential backoff - Input validation schemas, file size limits, global 401 interceptor - Docker compose with backend + frontend (nginx) services