fix: frontend Docker build output to ./dist instead of ../backend/static

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Dockerfile.frontend

@@ -5,7 +5,8 @@ WORKDIR /app
 COPY web/frontend/package.json web/frontend/package-lock.json* ./
 RUN npm install
 COPY web/frontend/ .
-RUN npm run build
+# Override outDir for Docker build (vite config uses ../backend/static for local dev)
+RUN npx vite build --outDir ./dist
 
 # Production stage
 FROM nginx:alpine