Implement relative paths for frontend API and WebSocket connections

- Created `.env.production` file to define relative paths for production deployment.
- Updated frontend API and WebSocket client to use environment variables for dynamic URL handling.
- Enhanced deployment scripts (`deploy-ubuntu.sh`, `start.sh`, `start.bat`) to generate `.env.production` automatically.
- Added `PRODUCTION_URLS.md` for documentation on production URL configuration and troubleshooting.

start.sh

@@ -48,6 +48,13 @@ echo ""
 
 # 4. Сборка frontend
 echo -e "${YELLOW}🔨 Сборка frontend...${NC}"
+
+# Создаем .env.production для production
+cat > .env.production << 'EOF'
+VITE_API_URL=/api
+VITE_WS_URL=
+EOF
+
 npm run build
 echo -e "${GREEN}✅ Frontend собран в backend/public${NC}"
 echo ""