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

frontend/Dockerfile

@@ -0,0 +1,10 @@
+FROM node:20-alpine AS builder
+WORKDIR /app/frontend
+COPY package*.json .
+RUN npm install
+COPY . .
+RUN npm run build
+
+FROM nginx:alpine
+COPY --from=builder /app/frontend/dist /usr/share/nginx/html
+EXPOSE 3014