feat(auth): implement multi-step authentication flow with UI

This commit replaces the placeholder login page with a comprehensive, multi-step authentication system. It introduces a new `AuthPage` that orchestrates the user flow between login, signup, and OTP verification.

- **Login Form**: Supports both email and WhatsApp credentials, with input validation and API integration.
- **Signup Form**: Includes fields for full name, email, and WhatsApp, with real-time password strength validation.
- **OTP Form**: Provides a view for users to verify their account after signup.
- **UI/UX**: The entire authentication experience is restyled with a new background, Poppins font, custom brand colors, and improved form components for a polished look and feel.
- **Dependencies**: Adds `axios` for handling API requests to the backend.

BREAKING CHANGE: The `LoginPage` component has been deleted and is replaced by the new `AuthPage` component. All references to `LoginPage` must be updated.

adventure-rental-app/package.json

@@ -10,6 +10,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "axios": "^1.11.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0"
   },