Add Docker build and run workflow

Dockerfile

@@ -0,0 +1,25 @@
+# syntax=docker/dockerfile:1
+
+FROM node:22-alpine AS build
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+COPY index.html vite.config.js ./
+COPY src ./src
+
+RUN npm run build
+
+FROM nginx:1.27-alpine
+
+ENV NOTES_API_UPSTREAM=http://host.docker.internal:8080
+
+COPY nginx.conf.template /etc/nginx/templates/default.conf.template
+COPY --from=build /app/dist /usr/share/nginx/html
+
+EXPOSE 80
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD wget -qO- http://127.0.0.1/ >/dev/null || exit 1