Add Dockerfile to simplify local setup and standardize development environment

[rahul810050]

The project currently relies on local environment setup (Node.js, npm versions,
system dependencies), which can lead to inconsistencies across machines.

Adding Docker support would:

• Standardize the development environment.
• Reduce onboarding friction for new contributors.
• Avoid Node/npm version mismatch issues.
• Make local setup and CI usage more predictable.

Proposed changes:

• Add a Dockerfile to build and run the application.
• Optionally expose the default development port.
• Support environment variables via .env or Docker arguments.
• Keep Docker usage optional (local setup remains supported).

This would improve developer experience and align the project with modern
best practices for frontend/admin platforms.