chore(docker): update ports and switch frontend to serve static files

- Change frontend port from 80 to 8847 and backend port from 3001 to 9173 in .env.example
- Replace nginx stage in frontend Dockerfile with node alpine and serve for static hosting
- Remove nginx.conf and related configuration for frontend static serving
- Update docker-compose ports and healthcheck URLs to match new port assignments
- Adjust server Dockerfile to expose new backend port 9173 and update healthcheck URL
- Create non-root user in frontend Dockerfile and run serve command on port 8847
- Update healthcheck commands to use wget on new ports for both frontend and backend

server/Dockerfile

@@ -35,9 +35,9 @@ RUN addgroup -g 1001 -S nodejs && \
     adduser -S nodejs -u 1001
 USER nodejs
 
-EXPOSE 3001
+EXPOSE 9173
 
 HEALTHCHECK --interval=30s --timeout=10s --start-period=10s --retries=3 \
-    CMD wget -q --spider http://localhost:3001/health || exit 1
+    CMD wget -q --spider http://localhost:9173/health || exit 1
 
 CMD ["node", "dist/index.js"]