Add docker

Dockerfile

@@ -0,0 +1,22 @@
+FROM node:20-alpine AS deps
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+FROM deps AS build
+WORKDIR /app
+COPY . .
+
+# Build-time API endpoint override; defaults handled in code.
+ARG VITE_API_URL
+ENV VITE_API_URL=${VITE_API_URL}
+
+RUN npm run build
+
+FROM nginx:1.27-alpine AS runtime
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /app/dist /usr/share/nginx/html
+
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]