feat(ui): polish error page when 404 (#943)

Adding link to home when it's 404 error.
![Capture
d’écran](https://github.com/user-attachments/assets/9a748d33-5135-4100-978a-f30d3067fcac)

Author: AugustinMauroy

frontend/routes/_error.tsx

@@ -17,13 +17,18 @@ export default function Error({ error }: { error: unknown }) {
         />
         <div class="w-full overflow-x-hidden relative flex justify-between flex-col flex-wrap">
           <div class="flex-top">
-            <header class="text-center px-8 py-[10vh]">
+            <header class="text-center px-8 py-[15vh]">
               <h1 class="font-extrabold text-5xl leading-10 tracking-tight text-gray-900">
                 {error.status}
               </h1>
               <h2 class="mt-4 sm:mt-5 font-light text-2xl text-center leading-tight text-gray-900">
                 {error.message}
               </h2>
+              {error.status === 404 && (
+                <a class="button-primary mt-4" href="/">
+                  Get back to safety
+                </a>
+              )}
             </header>
           </div>
         </div>