Issue #1: Add OAuth Login (Google/GitHub)

[Nel-ctrl]

Type: Feature
Priority: Medium
Linked Requirements: Req 1 (JWT or OAuth for Google/GitHub sign-in)

Description

Currently, the authentication system only supports email + password login. The requirements specify OAuth support for Google/GitHub sign-in as an alternative.

Acceptance Criteria

• Users can sign in with Google OAuth
• Users can sign in with GitHub OAuth
• OAuth tokens are securely exchanged for JWT tokens
• User email and name are auto-populated from OAuth provider
• Login page displays OAuth buttons
• Existing JWT flow still works (no breaking changes)

Tasks

• Set up Google OAuth credentials (Google Cloud Console)
• Set up GitHub OAuth credentials (GitHub Settings)
• Add OAuth libraries (e.g., passport-google-oauth20, passport-github2)
• Implement auth service OAuth endpoints
• Add OAuth redirect handling in frontend
• Add Google/GitHub buttons to LoginPage