Success Popup + Cookie-based Login Sync

[MUSKANNISHAD]

📌 Pull Request Summary

Implemented unified login flow with proper session handling and environment configuration.

🛠️ Type of Change

• Added a SuccessPopup for a cleaner login/signup experience.

• Fixed auth state conflicts: replaced localStorage usage in frontend with HTTP-only cookies from backend.

• Added .env.example as a template for environment variables to standardize setup across devs.- [ ] 🐛 Bug fix

• [✅] ✨ New feature
• [✅] 🧹 Code refactor
• [✅ ] 📄 Documentation update

🔗 Related Issue

Closes #784

✅ Checklist

Please confirm the following before submitting:

• [✅] I have tested my changes locally
• [✅] I have run npm run dev or similar to check code style
• [✅] I have updated documentation (if necessary)
• [✅] My code follows the project’s coding conventions
• [✅] I have merged the latest main or dev branch
• [✅] I have performed a self-review of my own code.
• [✅] My changes generate no new warnings or errors.
• [✅] I have commented my code, especially in hard-to-understand areas
• [✅] I have linked the related issue

📸 Screenshots (if applicable)

before=>

After=>

🧠 Additional Notes

• Anything else you want the reviewer to know.

• Frontend now relies on backend cookies for auth state.

• .env.example helps new developers quickly configure environment variables without exposing secrets.

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[MUSKANNISHAD]

I’ve reviewed the changes in this PR and verified that everything looks good. Authorized the deployment from the fork for preview purposes.