Troubleshoot the issue of missing backend instruction in README

[Areeba-Tahir-18]

This pull request addresses a documentation GAP where backend setup and run instructions were missing .

--> 𝗣𝗥𝗢𝗕𝗟𝗘𝗠
Previously, contributors and new users had difficulty understanding:

• How to start the backend service
• Where the backend entry point is located
• Which command should be used to run the backend locally

--> 𝗦𝗢𝗟𝗨𝗧𝗜𝗢𝗡
This update improves the README by:

• Adding clear backend setup and run instructions
• Clarifying the backend directory structure
• Helping new contributors get the backend running without trial-and-error

--> Here is the Proof of my Work or Contribution in filling this gap .

Kindly Review my Pull request @QuantumByte-01