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/src/AuthPage.jsx

@@ -0,0 +1,34 @@
+import React, { useState, useCallback } from 'react';
+import LoginForm from './LoginForm';
+import SignupForm from './SignupForm';
+import OtpForm from './OtpForm';
+
+const AuthPage = () => {
+  const [view, setView] = useState('login'); // 'login', 'signup', or 'otp'
+
+  const showSignup = useCallback(() => setView('signup'), []);
+  const showLogin = useCallback(() => setView('login'), []);
+  const showOtp = useCallback(() => setView('otp'), []);
+
+  const renderForm = () => {
+    switch (view) {
+      case 'signup':
+        return <SignupForm toggleForm={showLogin} onSuccess={showOtp} />;
+      case 'otp':
+        return <OtpForm />;
+      case 'login':
+      default:
+        return <LoginForm toggleForm={showSignup} onSuccess={showLogin} />;
+    }
+  };
+
+  return (
+    <div className="min-h-screen flex items-center justify-center p-4">
+      <div className="w-full max-w-md p-8 space-y-6 bg-black/30 backdrop-blur-xl rounded-2xl shadow-2xl">
+        {renderForm()}
+      </div>
+    </div>
+  );
+};
+
+export default AuthPage;