Let the web container write its fetch cache

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/Dockerfile

@@ -16,6 +16,8 @@ ENV NODE_ENV=production NEXT_TELEMETRY_DISABLED=1 PORT=3000 HOSTNAME=0.0.0.0
 COPY --from=build /app/.next/standalone ./
 COPY --from=build /app/.next/static ./.next/static
 COPY --from=build /app/public ./public
+# Next.js caches fetched data here at runtime (portrait proxy).
+RUN mkdir -p .next/cache && chown -R node:node .next/cache
 USER node
 EXPOSE 3000
 CMD ["node", "server.js"]