feat: estrutura inicial do gerenciador de subdomínios

- backend Express com endpoints Hostinger DNS API
- frontend React+Vite+Tailwind com card de API key
- docker-compose (frontend:3014, backend:8019, nginx:8021)
- Traefik label para subdominio.clube67.com

backend/Dockerfile

@@ -0,0 +1,7 @@
+FROM node:20-alpine
+WORKDIR /app
+COPY package.json .
+RUN npm install
+COPY . .
+EXPOSE 8019
+CMD ["node", "server.js"]