Initial scaffold: tablet-checkin app

Staff-push guest check-in tablet. Fastify backend + React/Vite frontend,
three-tier auth (staff JWT, terminal API key, kiosk cookie), NewBook
integration via bookings_get/guests_update/bookings_update, pdfkit-based
regcard generation, marketing opt-in with Sendy/Mailchimp adapters.

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

frontend/Dockerfile

@@ -0,0 +1,13 @@
+FROM node:22-alpine AS build
+WORKDIR /app
+COPY package.json .
+RUN npm install
+COPY . .
+ARG VITE_HOTEL_NAME
+ENV VITE_HOTEL_NAME=$VITE_HOTEL_NAME
+RUN npm run build
+
+FROM nginx:alpine
+COPY --from=build /app/dist /usr/share/nginx/html/tablet-checkin
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80