Added Google OAuth sign up feature

[nihams]

Feature: Google OAuth Signup Integration
Added Google OAuth authentication to the signup page, allowing users to register with their Google account in one click.

Changes Made

• Added Google Sign-In button to signup form with consistent styling.Uses Passport.js with Google OAuth 2.0 strategy
• Added OAuth error handling to display user-friendly error messages
• Added error boundary to prevent React crashes during OAuth flow
• Enhanced OAuth error handling with detailed logging
• Made email sending non-blocking to prevent OAuth failures
• Added environment variable guards to prevent server crashes

Functionality

Consistent User Model: OAuth and manual users have consistent schema
Token Management: Secure JWT token handling for OAuth users
Error Handling: User-friendly error messages for OAuth failures
Fallback Mechanisms: Graceful handling of database permission issues

Testing

• Google OAuth flow works end-to-end
• Error handling for failed authentication
• Proper redirects and token management
• No breaking changes to existing functionality

Solves #550

[netlify]

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[github-actions]

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