Scaffold weather app: reception forecast display + shared internal API

- Backend: Fastify service polling Met Office DataHub (Global Spot: hourly,
  three-hourly, daily endpoints) with Open-Meteo fallback, hourly refresh.
  Reuses settings' hotel_location/met_office integrations (same pattern as
  hvac's lib/weather.js) rather than its own credential copy.
- Three display tiers stored in one forecast_points table: today (hourly),
  next 2 days (3-hourly), days 4-7 (plain daily) - 7 days total.
- Public /api/public/forecast (no auth) feeds the reception kiosk display;
  /api/internal/forecast (WEATHER_SECRET bearer) lets other apps read the
  stored forecast instead of polling providers themselves; /api/admin/*
  (normal JWT + settings cap) is the staff status/refresh page.
- Frontend: root / is the public full-screen Display (no AuthGate at all -
  first genuinely public app in the stack); /admin is the authed status
  page. apps.base_path is /weather/admin so the portal card opens the
  admin view directly, precedented by forecasting's history sub-route.
- LXC 131 / 10.10.10.131, registered in auth/src/db.js, push-to-forgejo.sh,
  and stack-init/install-stack.sh (deploy_weather + --only dispatch + full
  install chain).
- Typechecks and builds clean; not yet deployed.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/Dockerfile

@@ -0,0 +1,7 @@
+FROM node:22-alpine
+WORKDIR /app
+COPY package.json .
+RUN npm install --omit=dev
+COPY src ./src
+EXPOSE 3001
+CMD ["node", "src/index.js"]