Add root docker-compose and webapp Dockerfile/nginx for full-stack deployment

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

webapp/Dockerfile

@@ -0,0 +1,11 @@
+FROM node:22-alpine AS builder
+WORKDIR /app
+COPY package.json package-lock.json* ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+FROM nginx:alpine
+COPY --from=builder /app/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80