Add Docker Compose deployment with multi-stage build and nginx

Multi-stage Dockerfile builds the Vite app in Node 22 and serves static
assets from nginx:alpine. Includes gzip compression, SPA fallback routing,
immutable cache headers for hashed assets, and configurable port mapping
(default 8080). Deploy with `docker compose up -d`.

Dockerfile

@@ -0,0 +1,12 @@
+# Stage 1: Build
+FROM node:22-alpine AS build
+WORKDIR /build
+COPY app/ ./
+RUN npm ci
+RUN npx vite build
+
+# Stage 2: Serve
+FROM nginx:alpine
+COPY --from=build /build/dist /usr/share/nginx/html
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80