build: add nginx docker image and compose

Dockerfile implements multi-stage build: node:22-alpine for build
stage, nginx:1.27-alpine for production runtime. nginx.conf provides
SPA routing with gzip compression and cache headers. docker-compose.yml
prepared for Tower Traefik integration with external network and Host
route. All files match specification verbatim.

Dockerfile

@@ -0,0 +1,10 @@
+FROM node:22-alpine AS build
+WORKDIR /app
+COPY package.json package-lock.json ./
+RUN npm ci
+COPY . .
+RUN npm run build
+
+FROM nginx:1.27-alpine
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /app/dist /usr/share/nginx/html