Add backend data aggregator and API proxy services

- update-data.js: cron job that aggregates Google Calendar ICS feeds
  (today + upcoming, node-ical), Netbird reachability, Gitea/GitLab
  commit stats and Open WebUI models into data.json
- server.js: small Node proxy behind nginx exposing /api/chat
  (Open WebUI completions), /api/gpu-stats and /api/ollama
- gitlab-relay.js: prepared HTTP relay for GitLab over a Netbird VPN
  (not wired up yet; the setup key was rejected by vpn.ixsol.at)
- docker-entrypoint.sh: starts updater in the background, API proxy,
  cron (15 min refresh) and nginx without blocking startup
- nginx: proxy locations + no-cache for data.json
- compose: TZ, token env wiring from .env, gpu-stats service
  (python + rocm-smi with device passthrough)
- dockerignore: keep .env out of the build context

Dockerfile

@@ -1,15 +1,27 @@
-# Lightweight static host for the homelab dashboard.
-# Builds a small nginx image that serves index.html + assets.
+# Dashboard: nginx static host + calendar/data updater + API proxy.
 FROM nginx:1.27-alpine
 
-# Copy the site (static files only — no build step needed)
+# Install Node.js and cron for the data updater.
+RUN apk add --no-cache nodejs dcron
+
+# Copy site assets.
 COPY index.html style.css script.js /usr/share/nginx/html/
+COPY icons /usr/share/nginx/html/icons
 COPY nginx.conf /etc/nginx/conf.d/default.conf
 
-# nginx listens on port 80
+# Backend scripts (node_modules included so the build works offline).
+COPY api /opt/dashboard
+
+# Cron refreshes the data feed every 15 minutes.
+RUN echo '*/15 * * * * cd /opt/dashboard && node update-data.js' > /etc/crontabs/root
+
+# Entrypoint: run updater once, start API proxy + cron, then nginx.
+COPY docker-entrypoint.sh /docker-entrypoint.sh
+RUN chmod +x /docker-entrypoint.sh
+
 EXPOSE 80
 
 HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
   CMD wget -q --spider http://127.0.0.1:80/ || exit 1
 
-CMD ["nginx", "-g", "daemon off;"]
+ENTRYPOINT ["/docker-entrypoint.sh"]