Add PropTypes validation to Navbar and CartDrawer

[ananyasingh180306-ctrl]

📋 What does this PR do?

Adds runtime prop validation using prop-types for the Navbar and CartDrawer components.

Changes made:

• Installed prop-types dependency
• Added PropTypes definitions to Navbar.jsx
• Added PropTypes definitions to CartDrawer.jsx

Benefits:

• Improves developer experience
• Makes expected component props easier to understand
• Provides runtime warnings when incorrect prop types are passed during development
• Helps prevent silent prop-related bugs

Closes #57
📋 What does this PR do?

Adds runtime prop validation using prop-types for the Navbar and CartDrawer components.

🧪 How was this tested?

• Installed prop-types successfully
• Started the application locally using npm run dev
• Verified the application loads without build errors
• Confirmed PropTypes definitions are present for all component props in Navbar.jsx and CartDrawer.jsx

📸 Screenshots (if UI changes)

No UI changes were made.

✅ Checklist

• I've read the CONTRIBUTING guide
• My code follows the project's style guidelines
• I've tested my changes locally
• I've linked the related issue
• I haven't introduced any new secrets or API keys