Login Signup page Added with Validation

[saburi004]

Related Issue

Closes #254

Summary

Implemented a complete authentication system with secure login/signup functionality, password validation, protected routes, and user-based data isolation. Added modern glassmorphism-themed authentication UI matching the existing application design.

Changes Made

Backend & Database Layers

• Updated database.js
• Updated server.js
• Added auth.js
• Updated csvDownload.router.js
• Updated csvDownload.controller.js

Frontend Layers

• Updated index.css
• Updated index.html
• Updated store.js
• Updated app.js
• Updated api.js
  • Added authentication header support for AI extraction requests

Testing

• Tested signup flow with validation rules
• Tested login/logout functionality
• Tested session expiration and automatic logout handling
• Tested frontend and backend integration locally

Screenshots

• Added login page UI
• Added signup page UI
• Added validation checklist interactions

Checklist

• Code follows project style
• Tested locally
• No unrelated changes included
• Documentation updated (if applicable)