[chore] landing: prod Dockerfile(SSG 빌드→nginx) 추가

landing/Dockerfile.prod

@@ -0,0 +1,13 @@
+# 프로덕션: SSG 빌드(ssr:false, prerender) → 정적 산출물(build/client)을 nginx 로 서빙.
+FROM node:22-slim AS build
+WORKDIR /app
+COPY package.json package-lock.json ./
+RUN npm install
+COPY . .
+RUN npm run build
+
+FROM nginx:alpine
+COPY --from=build /app/build/client /usr/share/nginx/html
+# 프리렌더 안 된 경로도 index.html 로 폴백(SPA).
+RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  location / { try_files $uri $uri/ /index.html; }\n}\n' > /etc/nginx/conf.d/default.conf
+EXPOSE 80