fix(docker): expand frontend build context to root so update-version.js is accessible

WORKDIR changed to /app/frontend so ../update-version.js resolves correctly.

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

frontend/Dockerfile

@@ -1,14 +1,16 @@
 # Stage 1: Build Vite React App
 FROM node:20-alpine AS builder
 WORKDIR /app
-COPY package*.json ./
+COPY update-version.js .
+COPY frontend/package*.json frontend/
+WORKDIR /app/frontend
 RUN npm install
-COPY . .
+COPY frontend/ .
 RUN npm run build
 
 # Stage 2: Serve static files with high-performance Nginx on port 3013
 FROM nginx:alpine
-COPY --from=builder /app/dist /usr/share/nginx/html
+COPY --from=builder /app/frontend/dist /usr/share/nginx/html
 # Simple internal Nginx routing for single-page React router stability
 RUN echo 'server { listen 3013; location / { root /usr/share/nginx/html; index index.html; try_files $uri $uri/ /index.html; } }' > /etc/nginx/conf.d/default.conf
 EXPOSE 3013