feat: integrate GitHub OAuth and optimize recommendations portal

[vansh2604-star]

Pull Request

Summary

Integrates GitHub OAuth 2.0 connection and personalization in the developer recommendations portal of RIVETO. This allows users to connect their personal GitHub accounts, bypassing shared backend API rate limits and enabling tailored issue recommendations.

Description

• Backend Auth Routes: Added /api/auth/github and /api/auth/github/callback routes using OAuth 2.0 flow to retrieve and store user access tokens, and /api/auth/github/profile to retrieve user information from the GitHub API.
• Token Storage & Encryption: Introduced an AES-256-CBC encryption helper using Node's native crypto module to securely store user credentials in the database, adding githubAccessToken to userModel.
• Personalized Recommendations: Updated the recommendation service to verify, decrypt, and pass the user's personal GitHub token under headers (falling back to GITHUB_TOKEN if not authenticated).
• UI Enhancements: Added an animated, modern "Connect GitHub" action button and a synchronized Profile Card showing connected status (username, avatar, repository count) to IssueRecommendations.jsx.

Related Issue

Fixes #479

Type of Change

• New feature
• UI/UX improvement

Checklist

• Code follows project guidelines
• Tested locally
• No console errors
• Documentation updated if required

[vansh2604-star]

I'm sorry for the inconvenience, and thank you for your patience.

[Nsanjayboruds]

@vansh2604-star RESLOVE THE CONFLITS

[vansh2604-star]

@Nsanjayboruds

Done! I've merged the latest changes and resolved the conflicts. Ready for review.

[Nsanjayboruds]

@vansh2604-star provide a screenrecording of your change

[vansh2604-star]

[vansh2604-star]

@Nsanjayboruds

Here are the screenshots showing the GitHub connection flow: