frontend deployment changes & stop prerendering (#7227)

* feat: frontend docker image

* build: tweak gc, disable prerendering

* feat: pass along UA

* fix: fallback to process.env

* build: remove this pr branch test

* fix: don't pin docker image ver

apps/frontend/Dockerfile

@@ -0,0 +1,30 @@
+# syntax=docker/dockerfile:1
+
+FROM node:24-slim
+
+LABEL org.opencontainers.image.source=https://github.com/modrinth/code
+LABEL org.opencontainers.image.title=frontend
+LABEL org.opencontainers.image.description="Modrinth website"
+LABEL org.opencontainers.image.licenses=AGPL-3.0-only
+
+RUN apt-get update \
+	&& apt-get install -y --no-install-recommends dumb-init \
+	&& rm -rf /var/lib/apt/lists/*
+
+ENV NODE_ENV=production
+ENV HOST=0.0.0.0
+ENV PORT=3000
+
+WORKDIR /app
+
+# Nitro bundles every runtime dependency into .output, so no node_modules is needed.
+COPY --chown=node:node .output ./.output
+
+USER node
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
+	CMD node -e "fetch('http://127.0.0.1:'+process.env.PORT+'/robots.txt').then(r=>process.exit(r.ok?0:1),()=>process.exit(1))"
+
+ENTRYPOINT ["dumb-init", "--"]
+CMD ["node", "/app/.output/server/index.mjs"]