feat: added docker support for backend

[SHIVAM-KUMAR-59]

Description

Dockerized the backend service and added a complete local development environment using Docker Compose.

This setup includes:

• Multi-stage Docker build for the backend service
• PostgreSQL and Redis containers
• Container networking between backend, database, and Redis
• Environment variable support through production environment configuration
• Prisma client generation and database schema synchronization inside containers
• Documentation updates for running the backend with Docker

Fixes #10

Type of Change

• New feature

How Has This Been Tested?

Verified the Dockerized setup locally by:

• Building the backend image successfully

• Starting PostgreSQL, Redis, and backend containers using Docker Compose

• Confirming database connectivity and Prisma schema synchronization

• Confirming Redis connectivity from the backend container

• Verifying environment variables are loaded correctly

• Testing API endpoints after container startup

• Existing tests pass

• Manual testing

Screenshots (if applicable)

N/A

Checklist

• My code follows the project's style guidelines
• I have performed a self-review
• I have added/updated documentation as needed
• My changes generate no new warnings
• Tests pass locally

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