Optimize Docker images and add .dockerignore for frontend and backend

[amanydv860]

Summary

This PR optimizes the Docker setup for both frontend and backend:

• Reduced Docker image sizes using multi-stage builds
• Added .dockerignore files to exclude unnecessary files (node_modules, .git, logs, etc.)
• Switched to Alpine base images for smaller footprints
• Updated docker-compose.yml to use registry images for faster deployment

Benefits

• Faster build times
• Smaller image sizes (frontend: ~178MB, backend: ~60-70MB)
• Cleaner production images without dev dependencies
• Easier to pull and run from Docker registry

Notes

• Frontend now runs on port 3000 inside container; mapped to 5173 locally in compose
• Backend connects to MongoDB using service name in compose network
• Environment variables are configurable via compose

This PR does not change application functionality, only Docker setup and deployment efficiency.