ci: HEALTHCHECK 추가 + git clone 토큰 로그 노출 방지

- Dockerfile에 nginx HEALTHCHECK 추가 (wget, 30s 간격)
- deploy 단계 git clone에 set +x / --quiet / 2>/dev/null 적용

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -13,4 +13,6 @@ FROM nginx:alpine
 COPY --from=builder /app/dist /usr/share/nginx/html
 COPY nginx.conf /etc/nginx/conf.d/default.conf
 EXPOSE 80
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
+  CMD wget --no-verbose --tries=1 --spider http://localhost/ || exit 1
 CMD ["nginx", "-g", "daemon off;"]