feat(api): implement chestny-znak web app with True API integration

- 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

backend/src/services/token-cache.ts

@@ -23,3 +23,7 @@ export function hasToken(): boolean {
 export function getTokenTTL(): number | undefined {
   return cache.getTtl(TOKEN_KEY)
 }
+
+export function invalidateToken(): void {
+  cache.del(TOKEN_KEY)
+}