state: Add a "Disconnect Wallet" button with proper state cleanup

[AlAfiz]

Description

Users can currently connect their wallet, but there is no obvious way for them to log out or disconnect from the dApp.
We need to add a dropdown menu attached to the wallet address in the navigation bar that contains a "Disconnect" option.
When clicked, it must completely clear the wallet address from the global state, clear any local storage caches tied to the user, and return the UI to the logged-out state.
This is a basic privacy and security requirement for any Web3 application.

Requirements

• Make the currently displayed Wallet Address in the Navbar clickable.
• When clicked, open a small popup menu just below it.
• Add a "Disconnect Wallet" button inside this menu, styled with a subtle red hover effect.
• Write an onClick handler that resets the walletAddress state to null and clears the user's recent token searches from localStorage.