fix: hover bg color change fixed using correct css var

frontend/src/Navigation.tsx

@@ -352,7 +352,7 @@ export default function Navigation({ navOpen, setNavOpen }: NavigationProps) {
             }}
           >
             <a href="/" className="flex gap-1.5">
-              <img className="mb-2 h-10" src={DocsGPT3} alt="DocsGPT Logo" />
+              <img className="h-10" src={DocsGPT3} alt="DocsGPT Logo" />
               <p className="my-auto text-2xl font-semibold">DocsGPT</p>
             </a>
           </div>