Fix frontend nginx to use Railway PORT variable

- Use envsubst to inject PORT at runtime
- Template nginx.conf with ${PORT} placeholder

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/Dockerfile

@@ -22,13 +22,15 @@ RUN npm run build
 # Production stage
 FROM nginx:alpine
 
-# Copy custom nginx config
-COPY nginx.conf /etc/nginx/conf.d/default.conf
+# Copy custom nginx config template
+COPY nginx.conf /etc/nginx/templates/default.conf.template
 
 # Copy built files from builder stage
 COPY --from=builder /app/dist /usr/share/nginx/html
 
-# Expose port
+# Railway uses PORT env variable (default to 80 for local)
+ENV PORT=80
 EXPOSE 80
 
-CMD ["nginx", "-g", "daemon off;"]
+# Use envsubst to replace ${PORT} in nginx config, then start nginx
+CMD sh -c "envsubst '\$PORT' < /etc/nginx/templates/default.conf.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'"

frontend/nginx.conf

@@ -1,5 +1,5 @@
 server {
-    listen 80;
+    listen ${PORT};
     server_name _;
     root /usr/share/nginx/html;
     index index.html;