- Dockerfile: 3-stage build (frontend npm build → backend go build → alpine runtime) - Frontend dist files served from disk at /app/frontend/dist - server.go: catch-all GET handler serves static files with SPA fallback to index.html - config.go: new server.frontend_dir option (env: SUB_STORE_SERVER_FRONTEND_DIR) - API routes (/api/*), download routes, and /health take priority over static serving