Fix Authentication Flow, Redirects, and Data Storage Issues

# 🧾 Fix Authentication, Redirects, and Data Storage Issues

## 📝 Description
Currently, there are issues with the **signup**, **login**, and **redirect flow** in the EventKonnect platform.
- After signing up or logging in, users are not redirected to the correct pages.
- User data is not being stored properly in the database after signup.
- Some session/auth states are not persisting correctly.

The goal is to ensure smooth authentication flow and accurate data handling in the database.

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## ✅ Acceptance Criteria
- [x] User signup should create a new record correctly in the database with all required fields.
- [x] User login should authenticate against the stored credentials.
- [x] Redirects after successful login/signup should lead to the correct dashboard or home page.
- [x] Invalid credentials or existing users should show appropriate error messages.
- [x] Session/auth state should persist correctly (consider localStorage, JWT, or cookies).
- [x] Logout should clear session/auth data properly.

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## 🧠 Possible Implementation Approach
1. Review and fix the signup and login API integration with the backend.
2. Verify that user details are stored correctly in the database (check schema and backend routes).
3. Implement proper authentication flow using JWT or session tokens.
4. Use React Router (or Next.js routing) for redirects after successful login/signup.
5. Add error handling and success messages for user actions.
6. Test the complete flow end-to-end.

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## 🧩 Tech Stack Reference
- Frontend: Next.js
- Backend: Node.js + Express
- Database: Firebase
- Authentication: JWT / Session-based