fix : removed hardcoded Render URL from CORS allowedOrigins

[tmdeveloper007]

Summary of What Has Been Done

The server.js file contained a hardcoded Render deployment URL in the CORS allowedOrigins array. This has been removed since the CORS configuration already reads from environment variables CORS_ORIGIN, CLIENT_ORIGIN, and FRONTEND_URL.

Changes Made

1. backend/src/server.js:
   • Removed the hardcoded string "https://dailyforge-frontend-lhjq.onrender.com" from the allowedOrigins array

Impact it Made

• CORS configuration now relies solely on environment variables
• No hardcoded production URLs in the codebase
• Cleaner and more environment-driven deployment configuration

Closes #2022

Note: Please assign this PR to the tmdeveloper007 account.