Persist prayer data to a mounted Docker volume via Express API

Replaces localStorage with a JSON-file backend (server.js). Prayers are
stored in /data/prayers.json, which is mounted as a named Docker volume so
data survives container restarts and rebuilds. React fetches from /api/prayers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DReRqHxSYuVfCzTzQGD9hZ

Dockerfile

@@ -5,7 +5,14 @@ RUN npm ci
 COPY . .
 RUN npm run build
 
-FROM nginx:alpine
-COPY --from=build /app/build /usr/share/nginx/html
-EXPOSE 80
-CMD ["nginx", "-g", "daemon off;"]
+FROM node:20-alpine
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci --omit=dev
+COPY server.js ./
+COPY --from=build /app/build ./build
+
+ENV DATA_DIR=/data
+VOLUME ["/data"]
+EXPOSE 4000
+CMD ["node", "server.js"]