Route storefront marketplace under /storefront

Replace the legacy /explore marketplace route with /storefront across the
storefront app and production routing.

- move the marketplace index page to the storefront root route
- move company and vehicle detail pages from /explore/* to /* internally
- update marketplace links, renter dashboard links, saved company links, and
  header navigation to target /storefront
- remove remaining explore route references and wording from storefront code
- configure production Traefik to route /storefront and strip the prefix before
  forwarding to the storefront service
- set the storefront production asset prefix to /storefront so Next chunks load
  from /storefront/_next instead of the shared root /_next path
- redirect locale entry paths such as /storefront/fr back to /storefront while
  persisting the selected language cookie
- update middleware tests for the locale redirect and adjusted redirect mock

Verification:
- npm run test --workspace @rentaldrivego/storefront
- npm run build --workspace @rentaldrivego/storefront

apps/storefront/src/components/StorefrontHeader.tsx

@@ -9,8 +9,8 @@ export type Theme = 'light' | 'dark'
 export type Language = 'en' | 'fr' | 'ar'
 
 type Dictionary = {
+  home: string
   storefront: string
-  explore: string
   signIn: string
   ownerSignIn: string
   theme: string
@@ -124,13 +124,13 @@ export default function StorefrontHeader({
               href="/"
               className="rounded-full px-2.5 py-1 text-[12px] font-medium text-stone-600 transition hover:bg-stone-100 hover:text-stone-900 dark:text-stone-300 dark:hover:bg-blue-900/40 dark:hover:text-stone-100 sm:px-4 sm:py-2 sm:text-sm"
             >
-              {dict.storefront}
+              {dict.home}
             </Link>
             <Link
-              href="/explore"
+              href="/storefront"
               className="rounded-full px-2.5 py-1 text-[12px] font-medium text-stone-600 transition hover:bg-stone-100 hover:text-stone-900 dark:text-stone-300 dark:hover:bg-blue-900/40 dark:hover:text-stone-100 sm:px-4 sm:py-2 sm:text-sm"
             >
-              {dict.explore}
+              {dict.storefront}
             </Link>
             <a
               href={signInHref}