Navbar is not responsive on smaller screens

Describe the issue
On mobile devices, the navbar items (Home, About, Tours, Login, Register) do not collapse into a hamburger menu. Instead, they overflow or wrap into multiple lines, breaking the layout.

To Reproduce
Steps to reproduce:
Open the website on a mobile device or resize the browser window.
Observe the navbar layout.
Notice that the navbar links do not collapse, and the layout looks broken.

Expected behavior
The navbar should be fully responsive. On smaller screens, the links should collapse into a hamburger menu that expands on click/tap.

Screenshots

Additional context
Making the navbar responsive will improve mobile usability and overall user experience.

Start by locating the navbar component and its associated styling in the React frontend, then reproduce the issue by resizing the browser to a mobile viewport. Check the existing navigation behavior before deciding how to connect the mobile menu toggle. Done means the links no longer overflow or wrap, and the hamburger menu expands and collapses reliably on smaller screens.

Written by the indexing model from the issue text.